Convertning from GCS_NAD83 to NAD83 State Plane PCS

[Matt Beal]

Hello, 

I am attempting to use the GUI to convert our LAS data, (LASinfo below) into our local state plane projected coordinate system. 

GeoKeyDirectoryTag version 1.1.0 number of keys 5

      key 1024 tiff_tag_location 0 count 1 value_offset 2 - GTModelTypeGeoKey: ModelTypeGeographic

      key 2048 tiff_tag_location 0 count 1 value_offset 4269 - GeographicTypeGeoKey: GCS_NAD83

      key 2054 tiff_tag_location 0 count 1 value_offset 9102 - GeogAngularUnitsGeoKey: Angular_Degree

      key 4096 tiff_tag_location 0 count 1 value_offset 5703 - VerticalCSTypeGeoKey: NAVD88 height (Reserved EPSG)

      key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter

The issue I am having is that when trying to define the existing projection under the projection drop down, I do not see GCS_NAD83 as an option. I only see the options for UTM, state plane NAD 83 (this is what we are looking to convert to, but our data is not currently in that projection), state plane NAD 27, longitude latitude, lamber conic conformal, transverse mercator, EPSG code (I have the epsg code for the current projection (4269) but it is not an option as far as I saw, and ECEF. 

I'm sure that I am missing something. I would greatly appreciate any assistance that could be provided!

[Matt Beal]

Well. I feel really dumb. I just realized that if you maximize the window, more options appear, particularly under the 'longitude latitude' setting. I was able to choose NAD83 from there. I'm now having a new issue. I've set the elevation unites to meter and the vertical datum to NAVD88. It is also asking me for a geoid, which I do not know and have no idea how to get it. I attempted to run it without a geoid set and I'm getting the followin message for each tile: WARNING: horizontal datum of source unspecified. assuming same as target. 

[Mark Levitski]

I am not a heavy user of LAStools but I think what you have as input is simply lat long, so pick the "longitude latitude" option. And since tbe datum is the same as your output (NAD83) it should convert without issues.

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[Matt Beal]

I've attached a screenshot to show the settings I used. In addition to that, here is the command line text in case that helps: 

"las2las -cpu64 -lof file_list.27300.txt -target_sp83 GA_W -target_feet -target_elevation_feet -odir "O:\2012\2012_LIDAR_Data\RAW_LiDAR_NOAA_2012\LAS_StatePlaneWest" -odix "_SPW" -olas -nad83 -longlat -vertical_navd88_geoid09"

 If I am understanding what you are saying, then the settings shown in my attachment should have worked. However I still got the message " WARNING: horizontal datum of source unspecified. assuming same as target." I even decided to ignore the message and see what the end results looked like. It did complete and the files it produced were in State plane 83 GA_W, however they were now being projected off the coast of South Carolina. I'm not really sure where to go from here. I've tried everything I can thing of in the four hours I have worked on this so far. 

 

[Mark Levitski]

Could be a units thing. Check those. Input looks like meters. 

On Fri, Aug 21, 2020, 12:44 PM Mark Levitski <northe...@gmail.com> wrote:

Source and target are not the same if I'm understanding you right.  Source is geographic and target is projected. Though they share the same datum, NAD83. 

You should be entering lat long and getting XY out the other end.

Forgive me,  busy and didn't look closely at all your details 

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[Matt Beal]

Yes. The elevation unit input is in meters. When I pull that data into a map, I can tell that it is in meters. I guess I'm not understanding what you are saying I should change on my inputs. 

[Kirk Waters - NOAA Federal]

Matthew,

Based on the naming, I'm guessing that is one of the files we host. I grabbed the first one on your list and ran your command (or close to it) and then pulled the result into global mapper. It looks like it's in the right place, or at least in Georgia. Screenshot below is zoomed out a bit to give location context. Near the corner of Walton, Barrow, and Oconee counties. The options from your command that I didn't give were the -cpu64 and -vertical_navd88_geoid09. I didn't give the second one because if it's the same data, it's in geoid12a.

So, my question is, what software are you using to look at the data that is putting it off the coast of SC? The reason I ask is because when I look at the georeferencing tags, it's got the same EPSG code for the projection when I run it as feet as when I leave it as meters (EPSG: 26967 for both). That code is Georgia West, but in meters. I'm guessing your software is ignoring the tag that says it's in feet and using just the EPSG code, therefore thinking it's meters when it's really in feet. For more fun and games like this, see this post.

For completeness, here's the command I ran:

las2las -target_sp83 GA_W -target_elevation_feet -target_feet -o tmp.laz -nad83 -longlat -i /san1/reef/lidar1_z/geoid12a/data/1420/20120923_GAW24451420.laz

I did not get a warning about datums. The URL for that file is https://coast.noaa.gov/htdata/ lidar1_z/geoid12a/data/1420/20120923_GAW24451420.laz

Kirk Waters, PhD, BJCP          | NOAA Office for Coastal Management

Applied Sciences Program      | 2234 South Hobson Ave
843-740-1227                          | Charleston, SC 29405    

coast.noaa.gov/digitalcoast

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[Martin Isenburg]

Hello,

Thank you, Kirk, for this detailed answer. It ***REALLY*** helps to always include a lasinfo report for one of your sample files (or a link to some example data) so we do not have to guess. You can generate a lasinfo report using the GUI settings (under output options choose '*_info.txt') or via the command line:

lasinfo -i my.laz -o my_info.txt

http://rapidlasso.com/lasinfo
http://lastools.org/download/lasinfo_README.txt

Regards,

Martin

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