Survey Methodology
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Map 6 Survey techniques and areas where used (100 m between ticks)

            Over a period of three years we used several field techniques for our survey. All surveys began with reconnaissance over paths 8-20 m apart and were usually followed by brush clearing. During our clearing, we removed low brush and small lower tree limbs. We seldom removed a sapling more than 5 cm in diameter, and we always surveyed around larger trees. Our surveys employed various kinds of equipment, depending on our requirements and resources:

            (1) electronic-distance-measuring laser theodolite (EDM total station);

            (2) optical transit and level rod;

            (3) hand-held compass and fiberglass measuring tape;

            (4) hand-held compass with distances paced on foot.  

            The accompanying site map above (Map 6) shows where each of these four methods was used.  In general, all large structures on the site were measured with the EDM laser theodolite, and numerous closed traverses were employed to assure survey accuracy.  Although the laser theodolite reports information to an accuracy of 1 mm, as a practical matter the accuracy of points taken with the laser theodolite is a few centimeters.  The lower-accuracy optical transit and level rod technique was accurate to about half a meter.  Compass and tape measurements are accurate only to within a meter or so, and paced measurements may have an accuracy no greater than 10%.

            When we surveyed larger structures, we surveyed the slump line, the apex, and, where visible, corners of existing wall lines, terraces, and stairways.  When we surveyed small structures such as house mounds, we recorded as much information as could be observed, but this frequently included no more than the perimeter of a rubble platform of jumbled fill stones and its elevation.  Our knowledge of the existing wall lines of structures was used to draw rectified diagrams of them on the maps.

            We also surveyed modern features where they were intermixed with ancient elements, and so our maps identify many existing houses, buildings, footpaths, and roads. Areas of the site destroyed by quarrying or bulldozing during construction of the modern highway in the 1960s are of particular interest at Muyil, and we recorded these on the maps. Muyil is known to have been used as a staging port for the chicle trade in the early part of this century (Mason 1927:41) and was on a ranch owned by General Juan Vega of Caste War fame during the late 1800s and into this century. We recorded numerous wall lines in one area of the site together with an improved pathway to the Muyil lagoon and believe these formed part of the Vega ranch. In conversations with Pedro Cobá Caamal, the site guardian, we learned of several thatched huts in the area of the ranch that had collapsed in Cobá C.'s lifetime. In sum, our mapping records prehispanic remains, nineteenth- and early twentieth-century remains and modern (ca. 1980-1990) features.

            After we recorded structures at the site by survey, we returned to sample many of the structures with stratigraphically controlled test pits. Most pits were in midden areas and provide a record of the use of the structure over time. A later chapter discusses the dating of the structures.

            When we surveyed the site center and its large structures in the 1987 field season with the EDM theodolite, we took pains to record accurate three-dimensional information, i.e., X-Y coordinates plus elevation. We used these elevations to prepare the accompanying contour map of the site and to mark the heights of structures on the detail maps (Appendix 5). Our later surveys of 1988 and 1990 did not record elevation data for the terrain beyond the site center, although our field notes do include the elevations above the natural terrain of house mounds and walls. We also recorded major elevation changes. Thus, while contour data are given for all the areas that we surveyed, the contours for areas outside the 1987 survey are estimates.  All elevations are given using the water level in the Muyil lagoon (at the end of the dry season - May) as datum — elevation 0 m.  The elevation of the Muyil lagoon is somewhat higher (on the order of 50-200 cm) than sea level at the Caribbean 12 km away, because there is a steady outflow of fresh water from the Muyil lagoon into the Chunyaxche lagoon and from the Chunyaxche lagoon through the stream called Cayo Venado to the brackish water behind the sand dunes at the Caribbean shore.

            Survey data were recorded in field notebooks and then keyed into computer files, usually the same day. Data from the EDM theodolite computer display provided X-, Y-, and Z-distance, distance in the X-Y plane, and line-of-sight (X-Y-Z) distance (all in mm), plus horizontal and vertical angles in degrees-minutes-seconds of arc. All seven items were recorded and keyed into the computer. Since the combination of seven values provides several ways to calculate the relevant distances and angles, computer processing by a program I wrote for the purpose was able to identify several kinds of errors due to misreading, misrecording, or miskeying the values. Ordinarily, an incorrect value could be directly corrected on the computer by referring to the field notes. Details of this data processing of field survey data are contained in Witschey (1988e). Data from other survey techniques was also recorded on a computer, frequently directly onto the master site map AutoCAD drawing file. Direct recording permitted us to use the variety of angular units, scaling, and rotation functions available in AutoCAD. Thus, we could readily enter compass readings and paces from a paced survey, and then use AutoCAD functions to scale paces to meters and to rotate compass readings from magnetic north to true north.

            The mapping process revealed much about the site. The following points are of special interest — they are summarized here and discussed in greater detail elsewhere:

            (1) We recorded remains of a sacbe system within the site. The sacbe extends from the plaza group of structures near the main highway to the tallest structure at the site (the Castillo, Structure 8K-13) and continues in the same direction down to the grasslands at the edge of the Muyil lagoon. The section of the sacbe to the west of the Castillo was sketched by the Mason-Spinden Expedition (Spinden 1926; Mason 1927:175), but a portion of it had been destroyed during construction of the coastal highway. A portion of the sacbe continuing to the east of the Castillo was recorded by Peissel (1963:286,288). Our reconnaissance and survey west of the highway was designed to look for any possible extension of the sacbe system to the west (we also looked to the north, toward Coba). No traces were found of any additional sacbes other than those shown on the map, and the Muyil sacbe ends a few meters east of the highway near the Entrance Plaza Group.

            (2) We found four large earthen mounds along a line extending northeast-southwest, parallel to the edge of the karstic shelf. These are possibly the remains of an earthwork that supported a perishable palisade forming a defensive line along the eastern (shore) side of the site, but we found no evidence to support this hypothesis. Two burials were found in one of these mounds.

            (3) We found in the western transect and in reconnaissance elsewhere that there is an extensive field wall system, associated with both house mounds and shrines, extending a considerable distance from the site. The occupation of these areas dates to the Late Postclassic, a time of general population growth along the east coast.

            (4) There are few organized rectangular groups of structures at Muyil. Exceptions are the Entrance Plaza Group, where all the structures are grouped on a single platform, and the north end of the Great Platform, where there is a sunken rectangular plaza with facing temple-pyramids. There is also a certain rectilinearity to the area immediately to the west of the Temple 8 walled precinct.

            (5) Settlement density declines as one travels outward from the site center. Large house mounds are densely clustered around the civic/religious/ceremonial architecture within about 350 m of the site center. Small house mounds are scattered infrequently beyond 600 m.

            (6) We did not find remains of a ball court.

            (7) Some small ceremonial structures are located at or beyond the perimeter of the densely occupied site center.

            (8) Several civic-ceremonial buildings and much of the sacbe system are oriented approximately 12° clockwise from the cardinal compass points.

            (9) There are sascaberas (sascab mines) at the perimeter of the depression in the site center close to the major structures.

            (10) There is a cave beneath Temple 8 (Structure 9K-1) which was utilized in preconquest times.

            (11) Numerous metates and fragments were found on the surface and are marked on the detail site maps which form Appendix 5.  

© Copyright 2000-2008 Walter R. T. Witschey   Page last updated Thursday, April 03, 2008