Conversions and Transformations

TxDOT will not accept any datum transformations for control. If a change to the NAD83 project datum is needed for comparison of old surveys, two (2) control points can be resurveyed (GPS or conventional) from references in the new datum. Then, a translation-rotation-scale can be done holding to the two (2) points common to both datums. Or, if original raw GPS data is available, it can be reprocessed holding the new datum coordinates rather than the original datum coordinates.
Both CORPSCON and AASHTOW Survey Data Management Systems (SDMS) are acceptable software programs for the mathematical conversion of:
  1. Metric to US Survey Foot (or visa-versa)
  2. SPC zones to adjoining SPC zones
  3. Universal Transverse Mercator (UTM) to SPCs and
  4. Latitude/Longitude to SPCs.
In addition to these strictly mathematical conversions, these software programs provide useable combined adjustment factors (CAF) at the specific location of a point if the elevation is included in the input.