Many CRS Definitions don't have useful range specifications

[Norm Olsen]

There are more than 4,000 CRS definitions in the coordsys.asc file which do not have a geographic useful range specified.

[Norm Olsen]

A 'ConsoleUtility' named csAddEpsgExtents was written which will add geographic extents to the coordsys.asc file in a manner which will enable reasonable 'diff' action to see what was done.

This new utility used three sources to apply geographic extents to the definitions in the coordsys.asc file: EPSG 7.09, a coordsys.asc file maintained by the author of CS-MAP prior to Open Source submission, and a simple algorithm which applies easily to UTM zones.

In the process, definitions in the "LEGACY" group were not altered. The result of executing this process is summarized:

• 6617 definitions in the coordsys.asc file
• 1764 were LEGACY definitions, no fix attempted
• 702 Geographic extents already in place, no change attempted
• 2235 Fixed with an extent extracted from EPSG 7.09
• 830 Fixed with a pre-open source Mentor definition
• 109 Fixed with standard UTM extent definition based on zone
• 977 Remain without a geographic extent specification, may need manual tweaking.

NOTE: that in the CS-MAP context, these extents are considered to be useful ranges, and not the designed range of useage. Thus, CS-MAP extents tend to be more liberal than EPSG extents. Thus the csAddEpsgExtents application increased the size of the EPSG extents by about 25% (12.5% in each direction). The expansion of geographic system definitions was limited to a maximum of 2 degrees.

[Norm Olsen]

As of this date (11 June 2014) the status of this issue is as follows (with regard to non-LEGACY definitions):

CRS Count	Description
12	which cross the +/- 180 degree crack which need to be examined.
1370	with no useful range and for which there is no EPSG correspondence
8	with no useful range for which there is an EPSG correspondence
1301	with a useful range but no EPSG correpsondence to check against
3283	with a useful range AND an EPSG correspondence to compare against

It appears that many in the second group are essentially the same as others but with a different datum and/or linear units, implying that a useful range can be programmatically extracted from an equivalent definition with a useful range. That will be the initial method of attack for this issue.

[Norm Olsen]

Useful Range Transfer Table

[Norm Olsen]

The above suggestion was implemented and produced about 700 additional useful range definitions by copying the definition of a very similar (i.e. same except for datum and/or units) to a CRS definition which did not have same. The table arrived at for these changes was attached.

As of this date (16 October 2014) the status of this issue is as follows (with regard to non-LEGACY definitions):

CRS Count	Description
12	which cross the +/- 180 degree crack which need to be examined.
660	with no useful range and for which there is no EPSG correspondence
8	with no useful range for which there is an EPSG correspondence
2132	with a useful range but no EPSG correpsondence to check against
2931	with a useful range AND an EPSG correspondence to compare against
150	major difference between CsMap and EPSG definitions

[Don't know why tje 3283 number dropped down to 2931. Suspect this is due to improvements to the Useful Range Report from which these numbers were extracted.]

Next step, I guess, is to manually generate a table of 660 CRS names and associated EPSG Area Codes, and then programmatically extract useful range definitions from the EPSG dataset Area Table.

[Norm Olsen]

As of this date (17Nov2014) a console utility, csUsefulRangeXfer.cpp, has been written and used to extract from the 8.5 EPSG Parameter Dataset the "Area of Use" for some 60 CRS definitions in the Coordinate System Dictionary deemed to be in sufficient disagreement with the corresponding EPOSG definition. The changes were submitted to SVN and produced revision 2575.

Also, the code which uses the useful range has been examined and it has been determined that the specification which cross the 180 degree West longitude meridian are formulated correctly.

Thus, with our submission which produced revision 2575, our task is recolver to deling with the 660 definitions for which there is no Useful Range definition and for which there is no EPSG definition from wehich to extract same.