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Beginning with Version 24.0, TPC TPC includes the following two PRJ files
•EPSG: 3857 projected grid coordinates (meters or feet)
•EPSG: 4326 geographical coordinates (decimal degrees latitude / longitude)
Both are shipped with TPC and can be used when choosing a CRS.
EPSG: 3857
EPSG:3857 is a Spherical Mercator projection coordinate system popularized by web services such as Google Maps and later Open Street Map.
You can think of these as grid coordinates.
It is the most common CRS for online maps, used by almost all free and commercial tile providers. See Open Street Maps Wiki.
EPSG: 4326
EPSG4326 is a common CRS among GIS enthusiasts. It uses a simple Equirectangular projection.
You can think of these as ground coordinates.
GIS users will think of this a being geographic coordinates. See Shape Coordinate Systems.
Google Earth uses this CRS.
More Specifically
•Google Earth is in a Geographic coordinate system with the wgs84 datum. (EPSG: 4326)
•Google Maps is in a projected coordinate system that is based on the wgs84 datum. (EPSG 3857)
•The data in Open Street Map database is stored in a gcs with units decimal degrees & datum of wgs84. (EPSG: 4326)
•The Open Street Map tiles and the WMS webservice, are in the projected coordinate system that is based on the wgs84 datum. (EPSG 3857)
Sharing TPC Survey Data
As a rule, you will want to choose a CRS for your TPC survey that meets the requirements of the project, like the NAD 83 (epoch 2011). Then, share data with Google Earth and GIS via geodetic positions (latitude and longitude). They are then free to generate coordinates based on their internal coordinate systems.
For mapping apps that use grid coordinates, TPC provides several tools to transform your coordinates from one CRS to another. You can transform to their CRS when exporting to them and transform back to your survey's CRS when importing from them. See Transforming Coordinates.
Calibrating Them to Your Survey
You can also share TPC survey data via a calibration. See Calibrating Google Earth Data.
Related Topics
Coordinate Reference Systems
PRJ Files
Choosing a Coordinate Reference System
Transforming Coordinates
Calibrating Google Earth Data
Shape Coordinate Systems
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