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. (http://oceanservice.noaa.gov/facts/geodesy.html)”.