Global Mapper v25.0

ESRI vs EPSG

RobertR
RobertR GlobalMapper Fan!Trusted User
edited May 2011 in Projection Questions
Hello all,

Nowadays I am dealing with some problems regarding these types of projections. Usually I get the projection codes from http://spatialreference.org ;

The issue is that I would like to use EPSG codes but I have problems when I try to match the ESRI code with its corespondent EPSG code (I always open the ESRI prj file and then I try to find the EPSG code which has a similar prj file);

Does anyone know an easy way to find the EPSG code for a specific county from US?

Thank you,

Comments

  • global_mapper
    global_mapper Administrator
    edited April 2011
    I'm not sure what you mean for the EPSG code for a particular county. EPSG codes are associated with a particular coordinate system definition, including projection, datum, and units. There might be several different coordinate systems in common use for a particular county, so there isn't a 1:1 mapping between an EPSG code and a county. For the US counties do have what is called a FIPS code defining the county, but that doesn't have anything to do with a projection.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • RobertR
    RobertR GlobalMapper Fan! Trusted User
    edited April 2011
    Hello,
    Yes, I am sorry, what I wanted to say is that I work with different counties all the time and first I look for the ESRI code by looking at the parcel shapefile prj.
    Then, based on the same prj I am trying to find the EPSG code for that specific ESRI code.
    I am doing this just because it seems that EPSG codes work better with mapserver while when using the ESRI codes I have errors all the time.
    So i guess my question would be: Is there a way to find the EPSG code for an ESRI code?!
    Thank you,
  • global_mapper
    global_mapper Administrator
    edited April 2011
    Do you have an example Shapefile PRJ with the ESRI codes that you are talking about? I'm not familiar with any special ESRI projection codes, they should be using the standard EPSG codes in their PRJ files as well.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • RobertR
    RobertR GlobalMapper Fan! Trusted User
    edited April 2011
    Well, let's take for eg this proj code:

    PROJCS["NAD_1983_StatePlane_Pennsylvania_North_FIPS_3701_Feet",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",1968500.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-77.75],PARAMETER["Standard_Parallel_1",40.88333333333333],PARAMETER["Standard_Parallel_2",41.95],PARAMETER["Latitude_Of_Origin",40.16666666666666],UNIT["Foot_US",0.3048006096012192]]

    My current method to find the EPSG code is:
    1. I search on http://spatialreference.org for StatePlane_Pennsylvania_North_FIPS_3701_Feet
    2. The search returns "ESRI:102728". Ok, I have the ESRI code but I want an EPSG code, so:
    3. I change the search words to "Pennsylvania North";
    4. The website returns several EPSG codes and here I usually exclude a few (those that are not using 'feet' as a measurment unit) and lookup the prj code for the ones left;

    This is how I finally find the EPSG code and I was just wondering if there is an easier way of doing this if you have the shapefile prj and you need the EPSG code.

    Sorry for the ambiguous explanations. I guess in the end there is a simple way of solving this issue but I seem to lack the experience. :D
  • global_mapper
    global_mapper Administrator
    edited April 2011
    If you have the Shapefile loaded in Global Mapper (the .prj file should automatically be read), just open the Metadata dialog for the layer from the Control Center and one of the listed items will be EPSG_CODE if the projection matches an EPSG code that Global Mapper knows about.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • RobertR
    RobertR GlobalMapper Fan! Trusted User
    edited April 2011
    Perfect. I did not know about this possibility. For this specific case, the EPSG code is not listed but I am sure it will be useful in other situations.

    Thanks a ton! :)

    Kind regards,
  • RobertR
    RobertR GlobalMapper Fan! Trusted User
    edited April 2011
    Later update

    I just checked this method for a parcel layer in Cattaraugus county,NY and in the Metadata section I have the 2261 EPSG code;

    I think this is not correct as EPSG 2261 corresponds to NAD83 / New York Central (ftUS) while the parcel layer prj file (see below) has a NAD83 / New York West (ftUS) prj which should be the correspondent to EPSG: 2262;

    "PROJCS["NAD_1983_StatePlane_New_York_West_FIPS_3103_Feet",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",1148291.666666667],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-78.58333333333333],PARAMETER["Scale_Factor",0.9999375],PARAMETER["Latitude_Of_Origin",40.0],UNIT["Foot_US",0.3048006096012192]],VERTCS["NAD_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137.0,298.257222101]],PARAMETER["Vertical_Shift",0.0],PARAMETER["Direction",1.0],UNIT["Meter",1.0]]"


    Sorry to bother you with this but I thought that maybe this could help.
  • global_mapper
    global_mapper Administrator
    edited April 2011
    Oops that is an error in the EPSG database in Global Mapper. Both NY Central and West were assigned to 2261. I have corrected the West zone to be 2262. I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with the change for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • RobertR
    RobertR GlobalMapper Fan! Trusted User
    edited May 2011
    Mike,

    If I am not asking too much, can you please tell me about the methods used to determine the EPSG code (by GlobalMapper I mean);

    (what parameters does it use to determine this and to which database does it connect etc.)

    Thanks for the support,
  • global_mapper
    global_mapper Administrator
    edited May 2011
    Global Mapper has a built-in database of EPSG codes that lists each supported EPSG code and the projection, datum, units, and set of projection parameters that it corresponds to. So when you try and determine the EPSG code for a projection Global Mapper just checks a projection definition against each EPSG code's projection until it finds a match.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • RobertR
    RobertR GlobalMapper Fan! Trusted User
    edited May 2011
    Hello,

    For our automated system we're gonna use use http://prj2epsg.org to retrieve the epsg codes.
    The site also exposes a service for development purposes, maybe it's of some use to you.
    Thank you