Geodetic Consulting Services: Untangle the Gordian Knot of Geospatial Information

What happens when your GIS digital aerial image from 2005, your GPS field data from last week (say manhole covers), and your road vectors purchased from a third party vendor, don’t line up?  A manhole cover is on someone’s front porch and the roads line up with the house roof tops?  CompassData’s trained Geodesists can help!


Example of a photo-identifiable ground control point acquired as part of a GIS Project in Ulaanbaatar, Mongolia.

CompassData can ensure that your GIS data elements are assigned an appropriate hierarchy of geographic location importance and are (if desired) held tight to precise Ground Control Points with Geodetic Consulting Services.  These GCPs can be adjusted to a geographic position relative to the time frame of the most important data layer (for example the image from 2005), or the data layers can be adjusted to the time frame the GCP was calculated to (e.g. 2002).  Other data elements that have less inherent accuracy (e.g. the manhole cover collected with a handheld GPS) can then be adjusted to the location of the higher level data elements (e.g. move the GIS data point “manhole  cover” over the manhole seen in the image).


Example of a laser point cloud image, San Francisco City Hall in San Francisco, CA. CompassData is well versed in validating the accuracy of geographical locations using a variety of geodetic techniques.

“Many organizations use geodesy to map the U.S. shoreline, determine land boundaries, and improve transportation and navigation safety. To measure points on the Earth’s surface, geodesists assign coordinates (similar to a unique address) to points all over the Earth. In the past, geodesists determined the coordinates of points by using Earth-based surveying tools to measure the distances between points. Today, geodesists use space-based tools like the Global Positioning System (GPS) to measure points on the Earth’s surface. (”.

Geodetic Consulting Services

Geodesy or Geodetics deals with the “measurement and representation of the Earth in a three dimensional, time-varying space”. GIS users and creators want to be able to say with some measure of confidence “the (runway, office building, police car, broken water main, etc.) is “here” (Latitude / Longitude, or other map units).

But “here” is typically a challenging concept; digital map data in a GIS must be in a unified map reference grid projected onto a generalized representation of the Earth’s surface called a reference ellipsoid.

For more information on Geodetic Consulting