GIS Library for Lazarus

[MarkMLl]

So, is this an issue with WGS84.pas, or am I misunderstanding something about GIS coordinates?  I have no survey training, so this latter is a real possibility.

In the interest of resolving this relatively quickly, I would suggest that a question on gis.stackexchange.com phrased like "I am using a software library which appears to use this sign convention: is this compliant with WGS84?" is in order.

MarkMLl

[Mike.Cornflake]

It seems to me that it is necessary to check the formulas for the use of x and y.

Nice.  I see what you're saying now.  Thanks

OK, I'll start trying to debug WGS84.pas.

[Mike.Cornflake]

Got to the bottom of the oddities I saw.  Don't understand the why, but it's deliberate code in two spots.  Here's one.

Code: Pascal  [Select][+][-]

1.   if UTM.southhemi then UTM.Y:=UTM.Y*-1;
2.  
3.   // reversal of UTM-X and UTM-Y to geodetic orientation
4.   // kasta om UTM-X och UTM-Y till geodetisk orientering
5.   t := UTM.X;
6.   UTM.X := UTM.Y;
7.   UTM.Y := t;

Original comment is in swedish.  I've used Google Translate to convert the commments.  Based on that I've added a property: TWGS88.IgnoreGeodeticOrientation.  It's false by default, which leaves the existing code to run.  Setting it True though stops the above conversion.   All values are now as I expect them.

[maurobio]

Hi,

I don't know if this is still of interest, but I have successfully used in a Lazarus/FPC application the library below (derived from Shapefile C Library, http://shapelib.maptools.org/):

https://web.archive.org/web/20070403193915/http://www.triplexware.huckfinn.de/shpapi.html

It is simple and fast.

Hope this helps.

Best regards,