Author Topic: Shape files display in the wrong geographic location  (Read 6076 times)

dgood71

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Shape files display in the wrong geographic location
« on: May 01, 2012, 05:21:04 PM »
It's probably just me not knowing what I'm doing, but when I load a shape file it shows up way off of where it should be geographically.  For instance, a shape file of state forest districts in Pennsylvania displays in Topofusion in South America.  It looks like the longitude is right, but the latitude is way off.  I did a quick search but didn't find anything on this.  Can someone please tell me what I'm doing wrong?  (I figure it's me because I never used shape files before)

BTW, I'm now on version 4.5 Pro if it makes any difference.  Thanks!


ScottMorris

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Re: Shape files display in the wrong geographic location
« Reply #1 on: May 02, 2012, 11:04:39 AM »
Hmm, it shouldn't be mixing up northern/southern hemisphere.  It does assume stuff about UTM zone if the shapefile is in that projection, resulting it the file being off to the east/west.  Can you attach or send me the shape file(s) (shape files are more than one file) and I'll have a look?

Thx.
Scott Morris - founder and co-author of TopoFusion
email: smorris@topofusion.com

dgood71

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Re: Shape files display in the wrong geographic location
« Reply #2 on: May 02, 2012, 12:01:09 PM »
The file can be downloaded here:  http://www.pasda.psu.edu/data/dcnr/DCNR_StateParks201109.zip

It's a shape file of all state park boundaries in Pennsylvania, but they show up in Topofusion in the northern part of South America.

BTW, a UTM zone boundary runs right through the middle of PA, but this is definitely a north-south issue, not east-west  (at least, not as far as I can tell being zoomed out as much as I am)

dgood71

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Re: Shape files display in the wrong geographic location
« Reply #3 on: May 02, 2012, 12:36:53 PM »
In looking at the data, it appears to have  been generated with ArcGIS 10, and the numbers it's coming up with for latitude and longitude are not even close.  It's like they're transformed into some other datum or somehow offset, rather than straight latitude and longitude.  Here's an example:

<rtept lat="1157776.34400910" lon="-575438.67574820"></rtept>
<rtept lat="1157783.01051301" lon="-575450.67574820"></rtept>
<rtept lat="1157790.34400910" lon="-575462.67574820"></rtept>
<rtept lat="1157797.67701691" lon="-575474.00924429"></rtept>
<rtept lat="1157804.34400910" lon="-575485.34274039"></rtept>

Not even close to valid lat/long pairs for PA.  I guess ArcGIS 10 stores this data in some oddball format?   I'm just trying to dump the shape file into a CSV of latitude/longitude pairs so I can build polygons of the state park boundaries.  The above output is from shp2text, a program that's supposed to dump the data from a shape file.  If that's the data that's being stored as latitude/longitude, then that's got to be one wierd datum they're using... or maybe it's offset somehow from a legitimate starting point.  I don't have ArcGIS so I can't load it up and see what's really going on.

dgood71

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Re: Shape files display in the wrong geographic location
« Reply #4 on: May 04, 2012, 09:39:01 AM »
After further digging, I've determined that the PA government uses a custom datum to reference their shape files.  Which means their files must be converted to a standardized datum in order to be of use to anyone else.  Being almost completely GIS stupid, I'm trying to figure out how to do this.  If I had ARCgis I could probably do it in a couple clicks, however I don't so it should be super fun trying to get this mess straightened out.

At least it's not a Topofusion issue.

ScottMorris

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Re: Shape files display in the wrong geographic location
« Reply #5 on: May 07, 2012, 09:59:09 PM »
Thanks for the update.  Those coordinates in the rtepts above look like "web spherical mercator" coordinates -- I am not sure shapefiles support that, but they may now.  TF's library might be a bit behind the times in that regard, though it seems like the latest should support it, if it's valid in a shapefile.
Scott Morris - founder and co-author of TopoFusion
email: smorris@topofusion.com