TheSwamp
CAD Forums => Vertically Challenged => Land Lubber / Geographically Positioned => Topic started by: cadtag on April 19, 2016, 12:51:46 PM
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I've done this before, and it worked. this time, i'm getting nonsense results. :crazy2:
The source gis data is a shp file from Northwest Florida Water Management District, -- supposedly 2' contours from lidar for Holmes Co.
The problems with my results is that I find it hard to believe than anywhere in N Florida has a 25' rise in 8 horizontal ft!.. And the elevations seem to be about three times higher than they should be. My supposed highest surface elevation of 433' is about 19 ft higher than the highest spot in the entire state!??! and a single 50 acre parcel is unlikely to have 150' of relief in that area.
Any ideas out there?
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meters?
and or send me link to your data source or the data to examine...
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found it....waiting for download and processing....will report
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they still have not sent me a download link...
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they still have not sent me a download link...
It does have a lag at times, but check your spam folder to be safe. The download link email is from a gmail account.
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When I grabbed the entire Holmes Co 2' contour shp file, the verticals were off, but the horizontal data was fine. The area landed where I expected, so it appears that the horizontal coordinates were being converted to feet properly, but elevation data stayed in meters.
I went back and tried with a custom area, picking a region close to the job, and with that area, both horizontal and vertical came in properly.
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they still have not sent me a download link...
It does have a lag at times, but check your spam folder to be safe. The download link email is from a gmail account.
nope nothing..I see our contract IT support is doing their job of keeping us from doing ours again
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When I grabbed the entire Holmes Co 2' contour shp file, the verticals were off, but the horizontal data was fine. The area landed where I expected, so it appears that the horizontal coordinates were being converted to feet properly, but elevation data stayed in meters.
I went back and tried with a custom area, picking a region close to the job, and with that area, both horizontal and vertical came in properly.
good to hear!
of note the data is also available
http://viewer.nationalmap.gov/basic/?howTo=true (http://viewer.nationalmap.gov/basic/?howTo=true)
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OK, from the file/link you sent me
There is an XML file- that honestly looks like it isn't 'complete'
however the key piece of information in there is this snip:
-<cordsysn>
<geogcsn Sync="TRUE">GCS_North_American_1983</geogcsn>
<projcsn Sync="TRUE">NAD_1983_UTM_Zone_16N</projcsn>
</cordsysn>
So that data is in Meters and one would want to set a file up on the correct coordinate system before importing the shp file data.
Then either make a surface in that file and export via land xml into a file on state plane ft - to work with it in feet
OR
Query the data into a file set in feet and then make the surface.
Will test the surface now....
further it appears there is NO 1ft contour elevation data so only the 2' contour lines are of use
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I had a similar issue with COGO Points I needed to build a Surface that came from 3rd party - ended up importing the COGO Points into my drawing (FL83-WF, US FT), and simply 'scaling' the COGO Point's elevation via LISP. :-D
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I think they fubarred something here...
the elevations in the DBF that go with the shape file are in feet....
so C3D is reading them and then scaling them and mucking up the actual elevation in the surface model
would have been so much better IF they had just given you the LAS file and not this shp file data.
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OK- bad data export/delivery method at work here.
I've studied the xml file included with the zip file pretty hard.
Nowhere in there do they tell the receiver that the data is UTM83-16F (US Survey Feet)
With that set in my destination file the map query produces good usable results and the elevations match what is in the dbf that accompanies the 2ft contour shp file.
Everything after that is good.
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http://viewer.nationalmap.gov/basic/?howTo=true (http://viewer.nationalmap.gov/basic/?howTo=true)
Cool.
Now I need to figure out how to work with a geopdf.
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Thanks Michael, I appreciate your looking into it. NWFWMD will send the LAS data, and I requested it for the county. So their system sent me download links --- looks like just under 650 files, all in 7zip format. I may try again and narrow down the requested area instead of the entire county. :2funny:
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http://viewer.nationalmap.gov/basic/?howTo=true (http://viewer.nationalmap.gov/basic/?howTo=true)
Cool.
Now I need to figure out how to work with a geopdf.
why? there are other more friendly data formats available from those guys.
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Thanks Michael, I appreciate your looking into it. NWFWMD will send the LAS data, and I requested it for the county. So their system sent me download links --- looks like just under 650 files, all in 7zip format. I may try again and narrow down the requested area instead of the entire county. :2funny:
or download only your area of interest from that national map view site...
or use map to query in only the contour lines in and around your subject site, and build your surface from that.
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http://viewer.nationalmap.gov/basic/?howTo=true (http://viewer.nationalmap.gov/basic/?howTo=true)
Cool.
Now I need to figure out how to work with a geopdf.
why? there are other more friendly data formats available from those guys.
All that showed up under "US TOPO" and "Historical Topographic Maps".
What should I be clicking on?
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see below...
also note that many of the Image products have elevation information embedded in them
QGIS has a utility to extract the elevation data from those images
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If working in Florida, this has been useful:
http://digir.fiu.edu/Lidar/lidarNew.php
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looks like they don't care about Holmes co :whistling: