"Flat Earth" Projection conversion

GeminiMindGeminiMind Global Mapper UserPosts: 19
edited September 2009 in Projection Questions
Currently, We are working a simulation project in which I need to convert projected elevation datasets(terrain) and corresponding layers(roads, building profiles, runways, etc) into a "Flat Earth" coordinate system.

Our GM v11 default workspace projection and datum settings:

Projection: UTM
Zone: 17 (Cleveland, OH)
Datum: WGS84
Planar Units: FEET (U.S.Survey)
Elevation: FEET
(Note: the maximum area we are working with covers 20 nautical miles diameter)

Most of the datasets we are using are provided with PRJ files so everything is layering properly. But - we have a few problems:

1) A couple of the layers/dataset provided were developed/created using a automated tools that are supposedly spitting out the files as WGS84 datum and "FLAT EARTH" projection. Therefore - they aren't lining up with our other layers. They are close but them slightly skewed and/or rotated. If we go back to those original DWG files and setup the projection to use "NAD 1983 HARN StatePlane Ohio South FIPS 3402 (US Feet).prj" the drawing lines up perfect with everything else.

-What is the equivalent to "Flat Earth" in GM's projection/datum settings?

-Does the projection setting "Orthographic" in GM project geospatial points on a flat plane aka "Flat Earth"?

2) When we try to convert a "State Plane, Geographic(Lat/Lon), UTM, or any other GM projection to "orthographic" projection, I keep getting a message in the status bar saying "Coordinate out of range" after selecting "Zoom selected Layer(s)" from the layer property sheet(popup menu). We are changing the default projection from "Geographic(lat/lon)" to "orthographic" via the configuration projection dialog tab.

-Is there something we need to do to allow "Orthographic" projection to convert properly?

Thanks for your help!

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2009
    The term "Flat Earth" might refer to an Orthographic projection or it might just mean unprojected lat/lon coordinates (the Geographic projection in Global Mapper). What do the actual XY coordinate values look like in the "Flat Earth" files?

    When you see the "Coordinate Out of Range" message in the status bar it typically means that the data was loaded with the incorrect projection and thus can't be converted to lat/lon coordinates for display on the status bar. This would also mean that the data couldn't be reprojected to another projection as it has to start out at a valid location to be reprojected.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • GeminiMindGeminiMind Global Mapper User Posts: 19
    edited September 2009
    This tool creates track areas based on very specific requirements. Generally, you give the tool (lat/lon) values for the beginning and end of straight lengths of track. The tool then builds all the markings, curb, accessory areas to specification required. The output datum is supposedly hard-wired to implement WGS84 datum. The one of the starting points to the track is specified to be the origin of the whole scene.

    After export, I looked at the XY values, they are just floating point values. The origin simply becomes (0,0). The other values are just regular Cartesian coordinates offset relative to the origin.

    When I am working with most datasets(dem, lidar, dwg, dgn, etc) they are projected using State Plane or UTM projections with either NAD83 or WGS84 datums.

    *How would you suggest taking all those GIS layers and projecting them to "flat earth" so that the generated tracks from this tool line up properly?

    Current Method(flawed)
    The current method I am using ends up having the tracks slightly skewed and rotated(3-6 degrees roughly) relative to the GIS layers. The current method is using UTM 17 as the projection. The values it outputs "under the hood" for lat/lon point values are offsets relative to the UTM zones origin. In GM, I create a point corresponding to the origin lat/lons. Using the GM set position function on said point, I get XY coordinates(the UTM origin offset). I export all my GIS data and the tool's generated data into my 3D package. Once in the 3D application I then translate my GIS data by the offset. Everthing lines perfect, except the slight skewing/rotation of the tracks.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2009
    Based on how it sounds like the application is adjusting your coordinates to a (0,0), you might try setting up the projection for that data as a Transverse Mercator or Orthographic projection with the central meridian and latitude set to the lat/lon of the 0,0 point and see if that works.

    If that isn't quite right, what you can do after loading the data in Global Mapper is to right-click on it, then select the option to modify the layer position. You can then enter control points to map the data from the current position to the desired position, which will then warp the data to match your control points.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • bisenbergerbisenberger Global Mapper User Posts: 55Trusted User
    Good info, as usual. :)
    Thanks Mike
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