SECTION 28.9. Analysis and Presentation of Data

Analysis and presentation of magnetometer and side-scan sonar data upon completion of a survey to locate submerged cultural resources are subject to the following, in addition to requirements under §26.24 of this title (relating to Reports Relating to Archeological Permits).

(1) If the survey is of sufficient duration, the magnetometer data will be corrected for diurnal variation using either separate data collected concurrently specifically for the purpose of diurnal corrections or through the use of an appropriate algorithm or mathematical formula.

(2) Magnetometer data will be presented on maps, aerial, or satellite imagery in a contour format. In order to facilitate review of this data by the THC, it should be presented at a scale sufficient for examination. Magnetic anomalies recommended for avoidance or investigation shall be illustrated at a scale and showing isolines at appropriate levels to illustrate the complexity and intensity of individual anomalies. Illustrating anomalies at this scale may require separate illustrations from the overall survey map.

(3) Maps illustrating magnetic anomalies will show the actual survey lines followed by the survey vessel and thus the position of each anomaly in relation to the survey lines.

(4) Positive and negative nodes of magnetic anomalies shall be indicated either by different colors of isolines (e.g. red for positive node, blue for negative node) or by variation in line type (e.g. hatched or dashed) for the negative isolines.

(5) Sonar data will be presented as a mosaic on maps, aerial, or satellite imagery. Sonar targets recommended for avoidance shall be presented at a scale suitable to show diagnostic attributes and may require separate illustrations from the overall survey map.

(6) The avoidance margin for significant magnetic anomalies and sonar targets, defined in 13 TAC Chapter 28, Rule §28.2, must be illustrated in the overall contour maps and sonar mosaics.

(7) A map of the survey area must be included in the survey report showing both the proposed survey lines and the actual survey lines.

(8) A table of anomalies and sonar targets recommended for avoidance or investigation, including the positions of those anomalies, or targets, shall be included in the report.

Source Note: The provisions of this §28.9 adopted to be effective August 21, 2008, 33 TexReg 6582; amended to be effective February 21, 2013, 38 TexReg 823; amended to be effective August 16, 2016, 41 TexReg 5997