The 1999 Poverty Point Mapping Project 

Final Report Submitted to the

Louisiana Division of Archaeology

DCRT Contract No. CFMS 540042/DCRT-0CD-99-06

 

Tristram R. Kidder

Department of Anthropology

Tulane University

 

Center for Archaeology

Tulane University

New Orleans, LA 70118

1999

Return to Current Research


The 1999 Poverty Point Mapping Project

Table of Contents

  • List of Figures

    List of Tables

  • Acknowledgements

    Introduction

  • Project Personnel
  • Methods

  • Equipment and Data Management

    Procedures

  • Horizontal and Vertical Controls

  • The Poverty Point Permanent Control System

    UTM Grid Conversion

    Vertical Controls

  • Results

  • Output Format and Scales
  • Conclusion

    References Cited


    List of Figures 

    Figure 1. Location of the Poverty Point site (16WC5), West Carroll Parish.

    Figure 2. Contour map of Poverty Point. The contours were created after deleting all modern features (roads, paths, etc.). Each data point acquired in 1999 is shown as a small red x.

    Figure 3. Contour map of the Poverty Point site including all modern features. Louisiana Highway 577 runs through the middle of the site.

    Figure 4. David Pickar using Nikon DTM420 Total Station Laser Transit with a TDS 48GX data collector (below laser transit).

    Figure 5. Conard hamilton mapping west side of Mound A.

    Figure 6. Map of Poverty Point showing elevations in different colors. Data from 1999 Poverty Point Mapping Project. Map by LSU CADGIS Lab, courtesy of Louisiana Division of Archaeology.

    Figure 7. Perspective map of Poverty Point looking from the east. Data from 1999 Poverty Point Mapping Project. Map by LSU CADGIS Lab, courtesy of Louisiana Division of Archaeology.

    Figure 8. Perspective map of Poverty Point looking from the south. Ballcourt Mound (Md. E) is at the bottom of the image. Data from 1999 Poverty Point Mapping Project. Map by LSU CADGIS Lab, courtesy of Louisiana Division of Archaeology.

    Figure 9. Map of Mound B. This map was generated by limiting the data universe of Figure 3 using SURFER and rescaling the resulting image.

    List of Tables

    Table 1. Example of Coordinate data (.CR5 File) Output from Data Collector.

    Table 2. Example of Raw Data (.RW5 File) Output from Data Collector.

    Table 3. Coordinates of Poverty Point Control Point Monuments.

    Table 4. Vertical Coordinates for Poverty Point Control Monuments.

    Acknowledgements

    The Poverty Point Mapping project is the result of the hard work and dedication of a number of individuals. The map is largely the product of the efforts and diligence of the mapping crew: Conard Hamilton, Daniel Stauber, and David Pickar. These students worked long hours both in the field and in the lab. Their skills as mapmakers are an important part of the legacy of research at Poverty Point. Anthony Ortman, Laurel Anderson, Jennifer Myer, and members of the Anthropology Student Union of Tulane University also contributed to the mapping and their efforts are greatly appreciated. Jason McBrayer, Assistant to the Director of the Center for Archaeology provided many valuable services to the project. Jason’s mastery of the computer allowed us to untangle many problems and to smoothly proceed from the field data to the final maps. Jason helped to make the contour maps used in this report.

    The project research was significantly aided by the advice and encouragement of Dr. Robert Connolly, Poverty Point Station Archaeologist, Louisiana Division of Archaeology, and Mr. Dennis LaBatt, Commemorative Area Manager, Louisiana Office of State Parks. These gentlemen provided essential information on the location of monuments, features, and landscape configurations. Without their assistance, our research would not have been possible. David Griffing of the Commemorative Area staff was also an invaluable resource and a wonderful and caring neighbor. We are grateful for the support of Mr. Billy Hale. Mr. Hale graciously provided us with access to his property on the east bank of Bayou Macon.

    The Poverty Point Mapping project was funded through the Ancient Mounds Heritage Area and Trails Advisory Commission and the Louisiana Division of Archaeology. Special thanks go to Representative Francis Thompson of Delhi for his enthusiastic support and encouragement. The Louisiana Division of Archaeology, Office of Culture, Recreation, and Tourism made this research possible. Our thanks go to Dr. Thomas Eubanks, State Archaeologist, and Nancy Hawkins, Archaeologist Manager, for their advice, encouragement, support, and persistence. We are also indebted to the Office of State Parks for their many services. The Poverty Point dorm was a wonderful place to stay. We could not have asked for better accommodations. Funding for equipment used during the Poverty Point Mapping Project came from the Louisiana Educational Quality Support Fund, award LEQSF (1997-1998) -ENH-TR-71.

    Lastly, we want to express our gratitude to Dr. Jon Gibson of the University of Southwestern Louisiana. The Poverty Point Mapping Project is the culmination of Jon's vision for an integrated map of Poverty Point. Jon recognized the need for the Poverty Point control system in 1983 and he saw to it that these monuments were placed at the site; without this effort, our project would not have been possible. Jon has also taken time to share his knowledge of the site and of the control system with us. We appreciate his labor and thank him for his kindness and cooperative spirit.


    Introduction

    The Poverty Point site (16WC5), West Carroll Parish, Louisiana (Figure 1), is one of the largest archaeological sites in North America. In addition to its size, Poverty Point is critical because it represents an early example of social and political complexity in North America. Indeed, the site is seen by some as a textbook case for the evolution of a non-agricultural, socially complex, culture (Bense 1994: 99-104; Fiedel 1992: 114-115). Despite its national and even international significance, the site has never been mapped in complete detail. Current large-scale representations of the site are drawn from tracings and interpretations of aerial photographs (Ford 1954; Ford and Webb 1956). These images combine data from air photography and interpolations based on ground observations (Webb 1982: Figure 9). No attempt has been made to rectify the aerial photographs nor has there been any systematic procedure for verifying observed features. The absence of an accurate map and coordinate system has been recognized as a critical research issue at Poverty Point since the early 1980s (Gibson 1984). In 1999, the Louisiana Division of Archaeology contracted the Center for Archaeology (CFA), Tulane University, to make a contour map of the Poverty Point site. More accurately, we were to map that part of the site contained within the boundaries of the Poverty Point State Commemorative Area.

    The research objectives of the 1999 Poverty Point Mapping Project were to accelerate the process of mapping the site at an appropriately detailed horizontal and vertical scale. The level of detail of our map is sufficient for producing a useable map at a horizontal scale of approximately 1:200 with a 20-cm contour interval. In addition, we were to provide digital data that could be used for creating computer images of the site.

    The Poverty Point Mapping project is in some ways the culmination of a project begun by Jon Gibson in the early 1980s. This project, referred to as the Ground Truth About Poverty Point (GTAPP), had as a central premise the need to understand the Poverty Point site by way of small-scale accurate topographic mapping (Gibson 1984, 1987). Although Gibson was unable to make a complete topographic map of the site, he did establish a horizontal and vertical geographic control system for Poverty Point. Our research in 1999 is a continuation of mapping and ground evaluation begun in 1983 (Gibson 1984). Gibson established a fixed series of control points across the site. In addition, he commissioned a large-scale topographic map of the central portion of the site. This map, which was constructed by using stereoscopic aerial photo mosaics, had a contour interval of 50 cm. Gibson acknowledged that while the horizontal scale of 1:1800 was appropriate, the vertical scale was too coarse-grained to serve the needs of researchers interested in assessing small-scale landscape features (Gibson 1984: 19-23).

     

     Figure 2. Contour map of Poverty Point. The contours were created after deleting all modern features (roads, paths, etc.). Each data point acquired in 1999 is shown as a small red x. 

      

    Figure 3. Contour map of the Poverty Point site including all modern features. Louisiana Highway 577 runs through the middle of the site.

    In addition to making a large-scale contour map of the central precinct, Gibson also began a program of contour mapping small segments of the site at 10 or 20-cm contour intervals (Gibson 1984: Figures 4, 9, 19). These maps are tied to the permanent control points and can be linked into the 1999 map by referencing their datum points. Gibson also commenced a program of assessing the nature of features revealed during mapping and surveying the site (Gibson 1984, 1987, 1989, 1990, 1993). This research began in 1983 and has continued over a number of field seasons.

    During January and part of February 1999, the CFA mapped the Poverty Point site. A crew of at least three archaeologists worked for six weeks to produce the map. During that time, they shot 10,418 points across the site (Figure 2). The map covers all of the known cultural features at the site with the exception of a small portion of the western end of the site (the "borrow pit") (Webb 1982: Figure 9). The map data acquired in 1999 is in digital format and has allowed us to produce a map of the site at twenty-centimeter (cm) contour intervals with a horizontal scale of approximately 1 inch equals 200 meters (m) (Figure 3). Because these data are in digital format, the map can be manipulated in any scale dimension. Maps can be produced using different contour intervals or different horizontal scales, and features can be deleted (or, for that matter, added) at the discretion of the user. Furthermore, the data may be used by any researcher with the appropriate software. The 1999 Poverty Point map represents the most comprehensive and accurate rendering of the site to date. The map is a valuable research tool in the present and will remain so in the future. This report will detail how the map was made and will discuss practical issues in the acquisition of data. This report will not concern itself with the interpretation of the findings of the Poverty Point Mapping Project.

    Project Personnel

    Dr. Tristram R. Kidder was Principal Investigator of the Poverty Point Mapping Project. Dr. Kidder spent the first week of the project in the field with the mapping crew and visited Poverty Point three times during the course of the fieldwork. He also supervised the process of translating and rotating the Poverty Point map data, as well as the rendering of the maps. Field personnel were Conard Hamilton, Daniel Stauber, and David Pickar. Mr. Hamilton and Mr. Stauber are graduate students in Anthropology at Tulane University. Both have extensive field experience, mostly in Mesoamerica, and both have considerable familiarity with the mapping equipment being used on this project. Mr. Stauber spent six weeks mapping at the Raffman site (16MA20) in the summer of 1998. Mr. Pickar graduated from the University of Oregon and worked on Poverty Point materials from the Poverty Point site prior to undertaking this project research. In addition to the full-time field crew, additional support was provided by visiting students from Tulane University working under supervision of Mr. Hamilton or Mr. Stauber.

    Methods

    Equipment and Data Management

    The Poverty Point Mapping Project used a Nikon DTM420 Total Station Laser Transit with a TDS 48GX data collector to acquire field data (Figure 4). At the completion of each day, the data were downloaded into an IBM 770-laptop computer using Survey Link software from Tripod Data Systems (Tripod Data Systems 1995). Data were downloaded in two forms. First, the data were transferred as a coordinate file. The coordinate file was translated from proprietary language used in the TDS GX48 data collector to ACII format using Survey Link software. The coordinate file consisted of five columns (point number, northing, easting, elevation, and point description). An example of a single page of coordinate file data is shown in Table 1. Each day's data was saved as a separate computer file, and in addition, a cumulative file was maintained. The data was also downloaded in "raw data" format. This format preserves all of the relevant survey data needed to reconstruct the coordinate file. Examples of a raw data file entry are shown in Table 2. Daily raw data files were preserved as separate files for each day. These files constitute the survey log and field notes. All files were backed up daily on removable 3.5-inch floppy discs. All of the data, both coordinate files and raw data files are available in digital format as well as a "hard copy." The digital data are presented as ASCII files and can be read by most word processing and data base files, as well as with current mapping software.

    The daily coordinate data were reviewed by importing the data into the computer-mapping program SURFER for Windows V. 6.0 (Golden Software 1997). A cumulative daily map was generated showing data points and contours. These files were printed, bound, and taken into the field each day. They served as a means of insuring adequate data collection by pinpointing data gaps, omissions, or gross errors. A field log was also maintained. This log recorded survey conditions, noted what kinds of shots were made, who was working and identified data that needed checking in the lab.


    Table 1. Example of Coordinate data (.CR5 File) Output from Data Collector

    Point No. Northing Easting Elevation Description

    5643, 5182.196305, 4714.855330, 30.128183, SWL4-5

    5644, 5193.699780, 4713.191525, 30.246635, SWL4-5

    5645, 5212.429274, 4710.387575, 30.274332, SWL4-5

    5646, 5206.268902, 4689.623875, 31.070219, R5

    5647, 5185.650664, 4686.321569, 31.093825, R5

    5648, 5168.339770, 4684.491197, 31.141871, R5

    5649, 5152.141945, 4685.435328, 31.199026, R5

    5650, 5133.448158, 4686.026675, 31.165062, R5

    5651, 5116.822956, 4689.740948, 31.223766, R5

    5652, 5102.628760, 4692.062241, 31.121617, R5

    5653, 5100.399978, 4677.573945, 30.809721, R5

    5654, 5110.335301, 4678.050600, 30.859271, R5

    5655, 5146.234163, 4679.105802, 30.950530, R5

    5657, 5162.857027, 4675.607896, 30.838013, R5

    5658, 5182.701658, 4675.333407, 30.823045, R5

    5659, 5194.701179, 4674.268971, 30.739611, R5

    5660, 5205.932263, 4671.433789, 30.665918, R5

    5661, 5204.486774, 4667.282787, 30.429684, SWL56

    5662, 5183.175232, 4664.706089, 30.521647, SWL56

    5663, 5171.160598, 4664.401302, 30.582741, SWL56

    5664, 5159.436920, 4663.324001, 30.535191, SWL56

    5665, 5146.489220, 4663.120505, 30.536912, SWL56

    5666, 5129.931670, 4664.660511, 30.530838, SWL56

    5667, 5117.109259, 4667.807410, 30.591894, SWL56

    5668, 5098.374723, 4668.258795, 30.572933, SWL56

    5669, 5085.720137, 4403.355625, 30.705666, PKROAD

    5670, 5081.625378, 4412.146469, 31.010495, MOUNDA

    5671, 5074.483170, 4430.629203, 34.412299, MOUNDA

    5673, 5069.886314, 4440.270016, 37.618463, MOUNDA

    5674, 5067.042468, 4448.425676, 40.480807, MOUNDA

    5675, 5064.800972, 4455.577803, 43.379106, MOUNDA

    5676, 5061.359650, 4462.141766, 46.986934, MOUNDA

    5677, 5059.680928, 4466.898044, 48.199689, MOUNDA

    5678, 5053.590877, 4468.059103, 49.027154, MOUNDA

    5679, 5055.884110, 4463.188016, 47.946095, MOUNDA

    5680, 5058.383330, 4454.560926, 43.751914, MOUND

    Procedures

    Mapping was generally carried out by a crew of three to four persons. In most instances, one person worked the total station while two individuals carried prism poles and identified points to be taken. The prism poles had changeable bases for different situations. When taking precise measures of specific fixed points we used a pointed ferrule while we used a flat "topographic shoe" for most shots. The instrument was set up over one of two kinds of points. Monuments designate fixed points established by Gibson in 1983. These monuments (five in total) have been geo-referenced to latitude and longitude and mark points in the Poverty Point coordinate system (Gibson 1984: 15-17). We also set up a number of Stations. A Station was designated as a temporary datum established by traverse or resection. Stations are marked by a ca. 40-cm long piece of steel rebar sunk into the ground with a yellow plastic cap marked "Tulane CFA" fitted over the top. Stations were labeled with the station number using indelible marker. A piece of flagging tape was also attached with the Station number written in marker.


    Table 2. Example of Raw Data (.RW5 File) Output from Data Collector

    JB,NMPPDATA2,DT1-21-99TM11:48:11.05

    MO,AD0,UN1,SF1.0000000,EC0,EO0.0

    SP,PN4376,N 5000.0000,E 5000.0000,EL100.0000,--TEST

    OC,OP4376,N 5000.0000,E 5000.0000,EL100.000,--TEST

    OC,OP38,N 4921.1349,E 4810.1002,EL29.797,--STATION38

    BK,OP38,BP5,BS300.5947,BC0.0000

    LS,HI1.504,HR1.620

    SS,OP38,FP4376,AR0.00000,ZE89.44200,SD221.584,--TEST

    SS,OP38,FP4376,AR202.48550,ZE90.39450,SD94.170,--MR

    SS,OP38,FP4377,AR197.30250,ZE90.08000,SD94.404,--MR

    SS,OP38,FP4378,AR202.27100,ZE91.06350,SD74.314,--MR

    SS,OP38,FP4379,AR191.02500,ZE90.11550,SD79.203,--MR

    SS,OP38,FP4380,AR197.47350,ZE91.01350,SD60.184,--MR

    SS,OP38,FP4381,AR182.38550,ZE89.56200,SD62.307,--MR

    SS,OP38,FP4382,AR194.27250,ZE91.06500,SD49.659,--MR

    SS,OP38,FP4383,AR180.29300,ZE90.09400,SD48.301,--MR

    SS,OP38,FP4384,AR189.04000,ZE91.21100,SD35.613,--MR

    SS,OP38,FP4385,AR175.07250,ZE90.12350,SD37.496,--MR

    SS,OP38,FP4386,AR181.01300,ZE91.25200,SD24.960,--MR

    SS,OP38,FP4387,AR168.34500,ZE90.15100,SD26.313,--MR

    SS,OP38,FP4388,AR173.40450,ZE91.40450,SD13.506,--MR

    SS,OP38,FP4389,AR157.25250,ZE90.36300,SD16.131,--MR

    SS,OP38,FP4390,AR139.50150,ZE89.47550,SD6.631,--MR

    SS,OP38,FP4391,AR232.57100,ZE94.30350,SD5.058,--MR

    SS,OP38,FP4392,AR212.03150,ZE94.07250,SD17.565,--MR

    SS,OP38,FP4393,AR214.11500,ZE92.28350,SD36.878,--MR

    SS,OP38,FP4394,AR209.44500,ZE91.51100,SD52.292,--MR

    SS,OP38,FP4395,AR209.14400,ZE91.32250,SD63.791,--MR

    SS,OP38,FP4396,AR209.18200,ZE91.17200,SD77.418,--MR

    SS,OP38,FP4397,AR209.55150,ZE91.03350,SD94.127,--MR

    SS,OP38,FP4398,AR228.26150,ZE92.38450,SD34.465,--MR

    SS,OP38,FP4399,AR256.10150,ZE93.02000,SD17.298,--MR

    SS,OP38,FP4400,AR263.10450,ZE92.10150,SD25.093,--MR

    SS,OP38,FP4401,AR246.42050,ZE92.39400,SD31.341,--MR

    SS,OP38,FP4402,AR220.17400,ZE91.53050,SD48.961,--MR

    SS,OP38,FP4403,AR236.07000,ZE92.06250,SD40.965,--MR

    SS,OP38,FP4404,AR220.26150,ZE91.33550,SD63.785,--MR

    Two types of point location routines were utilized: closed traverses and sideshots. Traverses were used to fix the locations of secondary datum points (Stations). Each closed traverse was begun at a known monument and ended at the same monument. The accuracy of each traverse could be measured using the Traverse routine in Survey Link. All traverses were accurate to specifications exceeding those established for class II second-order surveys (Schmidt and Rayner 1978; Sturgess and Carey 1987: Table 11.2). Once the traverse was completed, it was adjusted using the survey adjustment routine on the TDS 48GX data collector (Tripod Data Systems 1996). Traverse adjustment analyzes the error in the traverse (the difference between the starting and ending point) and closes the traverse by "correcting" errors so that the final closure is the same as the starting point. Traverse adjustment is an accepted survey procedure utilized to insure the highest accuracy possible (Tripod Data Systems 1995; Wolf 1987). In several instances, we had to establish secondary datum points using the two-point resection process. This procedure allows the instrument to be set up on an unknown point. The location of the instrument is established by shooting back on two separate known points. The instrument calculates its location by a process of triangulation. Because this procedure is not as accurate as a traverse (only because the angle error cannot be calculated or adjusted) we used it as infrequently as possible. Sideshots were the most common kind of data acquired. A sideshot is a point taken from a known location.

    Whenever a new instrument station was set up our procedure was to identify the new station by taking a backsight on a known monument (the ideal situation) or secondary datum. Once the backsight was established, we would then take a foresight on the same point. The foresight location could then be confirmed by checking the current location returned by the instrument with that already recorded in the field notebook. The backsight-foresight routine was utilized every time the machine was moved or turned off and on. Once the backsight was fixed, we would carry on with the sideshot routine to take X, Y, Z coordinate points.

    Our approach to mapping the Poverty Point site was to begin with the areas that were most heavily vegetated and most difficult to map. This process meant that we began in the northern and eastern portion of the site along Harlan Bayou. Our reasoning was that we would take advantage of extra labor (we had a crew of five for the first week) and enhanced visibility due to a series of frosts that had killed much of the ground and leaf cover. We proceeded from Harlan Bayou to the edge of Macon Ridge. Then we moved out into the site proper to shoot the ridges and other cultural features. We finished our work by shooting the features of Quincy Hale Gully on the south and east part of the site.

    Decisions about where to place points and what features to shoot were made in the field. Although our contract stipulated that we would shoot in any point that had a 50 cm elevation difference, in practice we often focused on far more subtle topographic variation. Points taken along Harlan Bayou, Bayou Macon, and Quincy Hale Gully were selected to demonstrate prevailing topography. We did not try to place points to discern every bit of topographic variation or to locate each rise or fall of the complex eroded topography of these localities.

    When we took points in the site proper we concentrated on establishing enough data to adequately and accurately represent features and landscape variation. Visible rises and depressions were mapped with points on (or in) the feature, as well as points nearby. We were conscious of the need to keep a relatively uniform data density. We also wanted to illustrate known or suspected features (ridges, aisles, and mounds) (Figure 5). To insure that the ridges were correctly portrayed we established a uniform procedure. Each ridge was mapped by placing a line of points along the crest of the ridge. When possible, two additional lines of points were placed along the slopes of the ridge, one on each side of the crest. A line of points was also placed in the lowest point adjacent to the ridge (the swales). In some locations, notably in the southern sector of the site, ridges were not discernable as elevations or depressions. In these instances we placed lines of points along the locations outlined by grass strips maintained by the Office of State Parks. The Park does not mow the projected locations of the ridges so that they could be followed by the mapping crew. The pattern of our mapping the ridges is illustrated in Figure 2. We also mapped all historic/modern features, including roads, paths, buildings, and other features. Buildings were located by at least one corner. The road through the park (Louisiana Highway 577) was mapped on both sides. The modern drainage ditch on either side of the road was also mapped. Paths were mapped along their centerline. Park boundaries (fences) were mapped when possible.

    We encountered relatively few difficulties during the mapping project. Due to very steep topography, the edge of Macon Ridge and its slope was difficult to acquire. Most of the slope of Macon Ridge and its contact with the bayou was shot from a resected point placed on the east bank of the bayou. The location of the water-land boundary along Bayou Macon is only approximate. The reason for this uncertainty is that the water level of Bayou Macon fluctuated. When we mapped the northeast corner of the site, the water level was relatively low. However, when we completed the mapping of the area at the mouth of Quincy Hale Gully, nearly six weeks later, water level had risen considerably. Similarly, the exact depth of Harlan Bayou is only approximate. Low water conditions prevailed when we mapped the eastern end of the bayou. However, by the time we began to map the bayou west of Highway 577 water level had risen dramatically.

    The map boundaries generally conform to the boundary of the State Commemorative Area. The only areas that we were unable to map are the area west of Mound A referred to as the borrow area (Webb 1982), and parts of the Commemorative Area north of Harlan Bayou and west of Highway 577. High water and dense brush made it impossible to complete the map in these regions. We also did not follow the boundary all the way to the northeast corner of the park. Here our map points terminate within 20 m of the actual boundary. The north side junction of Harlan Bayou and Bayou Macon was not reached. We were unable to locate a shot at the exact junction and had to settle for a point some five meters to the west.

    Horizontal and Vertical Controls

    The Poverty Point Permanent Control System

    Gibson established a horizontal and vertical geographic control system for the Poverty Point site in 1983 (Gibson 1984). This system is manifest by five survey monuments scattered within the Commemorative Area grounds. These five monuments (plus a sixth monument, located near Motley Mound beyond the Park boundaries) are the basis for the Poverty Point control system. Each point has an established latitude and longitude (and they are located in the 1927 State Plan Coordinate system), as well as a known elevation (Gibson 1984: 10-17, Tables 1-2). The monuments are fixed metal caps with a central dimple set in concrete. Each is marked JECA (John E. Chance and Associates) and each is numbered. In addition to being geo-referenced to latitude/longitude, these monuments are the datum points of the local Poverty Point grid system (Gibson 1984: Table 2). Monument 1 is the site datum for the grid system.

    The Poverty Point grid system has an imaginary local point of origin (0 meters northing, 0 meters easting) located south and west of the Poverty Point site. (Gibson's 1984 report lists the origin of the local system as 5000 northing, 5000 easting (Gibson 1984:11, Table 2), but this designation is incorrect. The proper local origin is 0 north and 0 east (Gibson, personal communication 1999)). Because the monuments were not fixed as control points until after Gibson had shot in a number of points around the site the coordinate system location of each monument "fossilized" Gibson's plane table grid (Gibson 1984). Gibson's plane table grid was not set to precise grid coordinates, and thus Monument 1 does not lie at 5000 N and 5000 E in the Poverty Point grid. The location of each monument according to Gibson's published data is given in Table 3. Table 3 also lists the coordinates of each monument as established by the Poverty Point Mapping Project. The small discrepancies between Gibson's grid locations (which should be read as the canonical coordinates), and our data are a result of survey errors and the difficulties in precisely relocating a point when surveying over large distances. We conducted a complete traverse of all five monuments in order to be certain that we were fixing our survey to the original Poverty Point grid coordinates. As can be seen in Table 3, our data agree very closely with Gibson's.

    Table 3. Coordinates of Poverty Point Control Point Monuments

     

    Location

     

    Latitude

     

    Longitude

     

    1983 Northing

     

    1983 Easting

     

    1999 Northing

     

    1999 Easting

     

    Monument 1

     

    N 32° 37' 59,074"

     

    W 91° 24' 20.172"

     

    4839.864

     

    4999.861

     

    4839.864

     

    4999.861

     

    Monument 2

     

    N 32° 38' 17.687"

     

    W 91° 24' 18.473"

     

    5414.895

     

    5000.00

     

    5414.860

     

    5000.012

     

    Monument 3

     

    N 32° 38' 25.853"

     

    W 91° 24' 45.807"

     

    5611.030

     

    4270.345

     

    5610.999

     

    4270.359

     

    Monument 4

     

    N 32° 38' 09.627"

     

    W 91° 24' 40.868"

     

    5122.554

     

    4437.035

     

    5122.545

     

    4437.043

     

    Monument 5

     

    N 32° 38' 00.239"

     

    W 91° 24' 34.738"

     

    4846.494

     

    4618.529

     

    4846.507

     

    4618.528

    Gibson's grid is aligned "approximately four degrees right [east] of Polaris north" (Gibson 1984: 11) and thus so too is our map grid. Although Gibson does not say so specifically, 4 degrees east of true north is the declination of magnetic north for northeast Louisiana as of 1982 (United States Geological Survey 1982). Therefore, it appears as if grid north on the Poverty Point map is nearly, if not completely, coincident with magnetic north.

    UTM Grid Conversion

    Prior to commencing mapping, we wanted to update the site datum to reflect the modern (1983) North American Datum (NAD) (the current reference standard) (Sturgess and Carey 1987). Conversion to NAD 83 was accomplished using a program available from the United States Geological Survey (United States Geological Survey 1983). The conversion updated the coordinate grid from NAD 1927 to NAD 1983. In addition, we attempted to convert the NAD 83 latitude and longitude data into UTM coordinates. Our rational was that UTM coordinates are more readily utilized and would allow us to align the Poverty Point local grid into a larger grid framework. We utilized one of a number of UTM conversion formulae available over the Internet. Once the conversions were accomplished in the lab, these data were taken into the field and the data were loaded into the data collector as the appropriate reference points.

    We began by setting up on Monument 2 and backsighting on Monument 1. We did not try to take a foresight on Monument 1. We then proceeded to run traverses across the northern and eastern part of the site, especially along the steeply eroded segments of Harlan Bayou. After a number of days of shooting points we set up again on monument 2 in order to begin a new traverse. By that time, we had begun the process of taking foresights on the points we used as backsights to insure accuracy. To our dismay, we discovered that we had mislocated our control points. Monument 1 was not where our converted data said it should be. Quick examination of the data revealed that our faith in the UTM conversion program was unwarranted. When we converted the data to UTM coordinates, we introduced an error at some point. Due to our miscalculation, the entire coordinate system was placed to the north of its actual location, and worse, none of the monuments was properly located. Our failure to use common sense to check the accuracy of the converted data was a major problem.

    Fortunately, no permanent damage was done. We ran a closed traverse of all of the fixed monuments using Monument 2 as datum. To do this traverse we had to establish an extra traverse point because there is no visibility between Monument 4 and Monument 5. Once the traverse was fixed, we knew the relative relationship among the monuments. Furthermore, because we knew the angle relationship of the original backsight from Monument 2 to Monument 1, we had an established rotational error. We then rotated and translated the data. All the points except Monument 1 were rotated by -3° 46' 38". Once rotated the points were translated to move the data down to the proper grid location. The initial (incorrect) data we used located Monument 1 at 5003.500 N and 5000.222 E. This placed the monument 163.636 m north and 0.361 m east of its actual location. Once the data were rotated around Monument 1 all the data were then moved "down" and to the "left" by these numbers. Thus, despite our initial mistake, the actual coordinates used to construct the Poverty Point map are accurate within the framework of tolerable error for a second order Class II survey (see Table 3). Note that the results of our map are still use NAD 27 as the control datum.

    Vertical Controls

    Vertical controls for the Poverty Point mapping project derive from data initially established by Gibson in 1983. At that time a traverse was run from a second order geodetic datum (referred to as "Dinny") located to the south of the Poverty Point site (Gibson 1984: 15). The elevation of "Dinny" was 27.76 m (NGVD 29). Each monument was tied into the elevation traverse (Gibson 1984: Table 2). After the establishment of the elevations relative to "Dinny" the National Geodetic Vertical Datum (NGVD) was revised in 1988 (Burkholder 1987). The conversion to the new NAVD (North American Vertical Datum) was a simple matter and did not require relocating (or mis-locating) the monuments. We converted from NGVD 29 to NAVD 88 utilizing a program from the U.S. Geological Survey (United States Geological Survey 1988). The results of the conversion can be seen in Table 4. The conversion back to NGVD 29 is a simple arithmetic operation of subtracting NGVD 29 from NAVD 88. Fundamentally, the change in vertical datum has little effect on the map.

    Table 4. Vertical Coordinates for Poverty Point Control Monuments

     

    Location

     

    NGVD 29 (in meters)

     

    NAVD 88 (in meters)

     

    Monument 1

     

    30.72

     

    30.67

     

    Monument 2

     

    30.57

     

    30.51

     

    Monument 3

     

    29.93

     

    29.87

     

    Monument 4

     

    30.37

     

    30.31

     

    Monument 5

     

    30.65

     

    30.59

    Results

    Output Format and Scales

    The results of the Poverty Point Mapping Project can be seen in Figures 2-7. These maps are only examples of what kinds of output can be produced using the 1999 mapping data. Note that Figures 2-3, and 7 all represent similar features, but at different scales. Also, note that Figures 2 and 3 represent different choices in selecting what data were actually presented. The contours of Figure 2 were drawn after modern features (roads, paths, parking lots, etc.) were deleted. Only after the contours were drawn did we overlay the actual points on the map. Figure 3 is a map with all of the points used to create the contours. Thus, in Figure 3, the path of Highway 577 is prominent through the middle of the site.

      

    Figure 6. Map of Poverty Point showing elevations in different colors. Data from 1999 Poverty Point Mapping Project. Map by LSU CADGIS Lab, courtesy of Louisiana Division of Archaeology.

      

    Figure 7. Perspective map of Poverty Point looking from the east. Data from 1999 Poverty Point Mapping Project. Map by LSU CADGIS Lab, courtesy of Louisiana Division of Archaeology.

     

    Figure 8. Perspective map of Poverty Point looking from the south. Ballcourt Mound (Md. E) is at the bottom of the image. Data from 1999 Poverty Point Mapping Project. Map by LSU CADGIS Lab, courtesy of Louisiana Division of Archaeology.

    A second example is a false color representation shown in Figure 6. This map, produced by the LSU CADGIS lab, is an example of one way that the digital data can be manipulated to produce different kinds of representations of the Poverty Point site. Figure 7 is a perspective view looking from the east. Figure 8 is a similar perspective view, but this time the view is from the south. These maps demonstrate some of the different ways of visualizing Poverty Point by using different perspectives and different colors to indicate elevation changes. Another example is a map of Mound B produced using the 1999 data (Figure 9). This map was produced by altering the map limits in SURFER and then rescaling the new data points. Essentially, it is a blow up of a small section of the larger map. These kinds of maps can be produced on demand for any segment of the map. Close up maps of segments of Poverty Point will be useful tools for fieldwork. Archaeologists can take accurate scale maps set to the Poverty Point grid into the field to locate features, place excavation units, or assess landscape configurations.

    Figure 9. Map of Mound B. This map was generated by limiting the data universe of Figure 3 using SURFER and rescaling the resulting image.

    Because the Poverty Point Mapping Project data are in a digital format, they can be manipulated in any number of ways. One important element of the map is that the map scale can be changed to suit the needs of each investigator. Horizontal scales can be altered without changing the contour interval as seen in Figures 2-3, and 9. Alternatively, vertical scales (contour intervals) can be changed while keeping the horizontal scale the same. Any number of combinations can be used. Similarly, the data are flexible because they can be updated and revised. Further work at the site can simply be plugged into the existing control file (assuming that Monument 1 is used as datum and that the Poverty Point grid designation is used). The Poverty Point map could be placed into larger-scale map of the entire region should such a mapping project ever be undertaken.

    Conclusion

    The legacy of the Poverty Point Mapping Project will only be realized in the future. As researchers utilize these new data, they are sure to change our understanding of the site. Archaeological fieldwork at the site can now achieve the objectives set by Gibson in 1983: "A single, uniform system was [is] needed to integrate data from scattered test excavations, aerial photogrammetric mapping, and remote sensing analyses. Such a system would [will] eliminate the old problem of noncomparability caused by having so many separate datum points and would insure locational compatibility for all future work" (Gibson 1984: 10).

    Beyond Gibson’s vision for a uniform and compatible map of Poverty Point, the 1999 Poverty Point Mapping Project data allows us to critically examine the site plan and its associated features. It is now possible to investigate questions of layout and site organization. For example, how many ridges are there at Poverty Point? Is there an aisle in the northern sector? How does "Ballcourt" mound relate to the organization of the site? Does the "Causeway" line up with any identifiable topographic features? These and many other questions can be addressed, at least in part, using the new map of Poverty Point. Having this map does not relieve us from the task of archaeologically assessing the features at the site, but it does allow us a previously unimaginable opportunity to understand and explore this massive and critically important archaeological site.


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