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Frequently Asked Questions on Geodetic Vertical and Water Level Datums for Engineers

Yes, but you may have to log on as an administrator
Corpscon, like Vertcon, only works for vertical conversions in the continuous United States (lower 48). This messages tells you that you are outside this boundary.
The program is making sure you have administrator privileges for correct installation.
Good question. We have only tested it for conversions within the US. Since the parameters for UTM conversions are for North America, Corpscon should work. Try the program on some known control points that have values listed in UTM and lat, long.
Corpscon has fixed decimal places in the output to prevent people from overestimating the accuracy. Conversions between some datums and some coordinate systems are not exact, only extrapolated between known points.
Corpscon only converts from NAD83 to NAD27 and reverse since it's based on NGS's NADCON. However the definition of NAD83 is close to WGS84 and therefore some will use NAD83 as WGS84. Be aware that is some cases the differences between NAD83 and WGS84 coordinates can differ as much as a meter.
In the new version, you only have to specify where the following fields are in the input file: Point Name, Lat, Long, and Elevation (if performing a vertical conversion). The remaining fields are carried over to the output file. For example, you have an input file with ptnumber, ptname, lat, long, elevation, field_code, and attribute. You would specify in the input side that the ptname is in field 2, the lat is in field 3, long in field 4 and elevation is in field 5. On the output side you specify the order of how you would like the converted coordinates and the input fields by specifying the number for each. So if you want the same order as above you specify ptname is field 2, coord_x is field 3, coord_y is field 4, elevation is field 5, Input Field 1 is field 1, Input Field 6 is field 6 and Input Field 7 is field 7.
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The State Plane Coordinate System (SPCS) is distorted, as are all projections. Dividing a distance between two points on the SPCS by the scale factor provides an approximation of the real distance, i.e., the distance measured on the ellipsoid, the surface a GPS works with.

A better approximation is the combined scale factor (combined factor). Dividing a SPCS distance by the combined scale factor approximates the length of a cord connecting the two points.

Scale factor is the ratio of an incremental distance measured on the ellipsoid to the distance on the State Plane grid, whereas combined scale factor is the ratio of the former distance to the distance on the ground.
Input longitude must be positive. East is east and west is west, except for Corpscon, where west is east. Try again, without the "-".
No, CORPSCON does not include conversions from/to UTM Zone 20 (Eastern Puerto Rico).
No, CORPSCON is only available via this Web site. If you have problems with the standard version (~10 MB), try downloading the minimum version and the VERTCON and geoid files separately.
No, CORPSCON does not convert from / to the WGS 84 datum. For most applications that CORPSCON is used for, NAD 83 is close enough. AGC has developed a program called GeoTrans which the National Geospatial-Intelligence Agency (NGA) now maintains. GeoTrans transforms between local geodetic datums and WGS 84.
1. Check to make sure that the longitude value(s) are positive. CORPSCON does not accept negative longitude values.
2. Are you in Alaska or Hawaii or Virgin Islands or Puerto Rico? Makes sure you have downloaded the files needed for these areas.
3. If you are using an input file, make sure that there is a carriage return after the last line of data in the file.
No, CORPSCON was only developed to work in these areas listed above. GeoTrans will do conversions in these areas, but does not support State Plane Coordinates or NADCON.
Make sure that CORPSCON was installed correctly (i.e. went through the install procedure) and not just copied from another computer or directory. CORPSCON places a file (Corpscon.ini) in the C:\Windows directory during installation which tells the software where (under what directory structure) it was installed.
No. Corpscon does not have a limit. However, you must have enough hard disk space for Corpscon to create a temporary file as well as your output file. For example, if your input file is 10MB, then you will need a minimum of 20MB of free hard disk space to perform the conversion.
CORPSCON is based on the NADCON and VERTCON algorithms developed by the National Geodetic Survey (NGS). The source code for NADCON and VERTCON is available on the NGS Homepage (

Make sure that you specified the User Defined Input File Field Specifications the same as your input file.

Input file contains:

Point name, Latitude, Longitude, Elevation, Feature Code

Make sure the User Defined Input File Field Specifications are set-up as:

User Defined Input File

Contact Us
Due to restricted resources, very limited assistance is available to non-Corps of Engineers users. AGC will maintain this web site and update the Frequently Asked Questions page. Please exhaust these web resources and the CORPSCON help files, before e-mailing the Point of Contact. AGC will provide assistance, where possible, although response to inquiries is not guaranteed.
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Corpscon POC