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Re: AI-GEOSTATS: Coordinate conversion near the poles

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  • Jim Bash
    The UTM grid system only extends to 80 degrees south (and 84 north). There is another system for polar areas, the Universal Polar Stereographic Grid System
    Message 1 of 5 , Feb 13, 2004
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      The UTM grid system only extends to 80 degrees south (and 84 north). There
      is another system for polar areas, the Universal Polar Stereographic Grid
      System (UPS). I've never had occassion to look at UPS so I can't say what
      projection is used but it, like the UTM system, is designed to have a
      certain accuracy within a zone. For UTM you can calculate distances and
      directions between any two points in a single zone to an accuracy of one
      meter in 2500 meters (people thing of UTM as being '1 meter resolution or
      accuracy'). I would assume UPS is similar.

      Good Luck!

      jim bash
      jbash@...

      On Fri, 13 Feb 2004, Ruben Roa Ureta wrote:

      > Hi list members:
      > I am now embarked in a project of fish stock assessment in the Falklands
      > using both hydroacoustics and fish density data from trawling, and of
      > course i want to use geostatistics for data analysis. I read in ai-geostat
      > archives a discussion not long ago about coordinate transformation before
      > statistical modelling to ensure proper distances. UTM coordinates were
      > recommended (the header was GeoR and memmory). The Falklands are quite
      > near the south pole so it seems to me at this location coordinate
      > conversion is a matter of relevance if i want to have a proper spatial
      > representation of the shape of the fish stock down there at the bottom of
      > the sea. The final purpose in our case is to integrate over the two
      > spatial dimensions of the fish density variable to arrive at a value of
      > total biomass. I would appreciate to have a confirmation that the UTM
      > coordinate system will account for the true shape of the Earth in my case
      > and thus i could proceed to geostatistical modelling after transforming
      > from latitude-longitude data to UTM. Thanks.
      > Ruben
      >
      > --
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      >

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    • Roger Bivand
      On Fri, 13 Feb 2004, Jim Bash wrote: Hold on. hold on! Look, Bergen, Norway is 60N, the Falklands, even with South Georgia, are not even 60S. I protest that
      Message 2 of 5 , Feb 14, 2004
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        On Fri, 13 Feb 2004, Jim Bash wrote:

        Hold on. hold on! Look, Bergen, Norway is 60N, the Falklands, even with
        South Georgia, are not even 60S. I protest that this isn't that near the
        poles, even the Arctic and Antarctic circles are at 66.6...N, and that's
        well within the 80N/S of UTM. The question was whether to transform from
        latlong to anything projected in order to do geostats, and the answer is
        yes, unless your geostats software itself calculates great circle
        distances from latlong coordinates (the fields package in R does, for
        example). So the answer is yes, use a projection of choice, UTM being a
        possibility (depending on the W-E extent of your data), or use software
        that respects that your data are latlong.

        Roger

        (writing from just North of 60N!!)

        >
        > The UTM grid system only extends to 80 degrees south (and 84 north). There
        > is another system for polar areas, the Universal Polar Stereographic Grid
        > System (UPS). I've never had occassion to look at UPS so I can't say what
        > projection is used but it, like the UTM system, is designed to have a
        > certain accuracy within a zone. For UTM you can calculate distances and
        > directions between any two points in a single zone to an accuracy of one
        > meter in 2500 meters (people thing of UTM as being '1 meter resolution or
        > accuracy'). I would assume UPS is similar.
        >
        > Good Luck!
        >
        > jim bash
        > jbash@...
        >
        > On Fri, 13 Feb 2004, Ruben Roa Ureta wrote:
        >
        > > Hi list members:
        > > I am now embarked in a project of fish stock assessment in the Falklands
        > > using both hydroacoustics and fish density data from trawling, and of
        > > course i want to use geostatistics for data analysis. I read in ai-geostat
        > > archives a discussion not long ago about coordinate transformation before
        > > statistical modelling to ensure proper distances. UTM coordinates were
        > > recommended (the header was GeoR and memmory). The Falklands are quite
        > > near the south pole so it seems to me at this location coordinate
        > > conversion is a matter of relevance if i want to have a proper spatial
        > > representation of the shape of the fish stock down there at the bottom of
        > > the sea. The final purpose in our case is to integrate over the two
        > > spatial dimensions of the fish density variable to arrive at a value of
        > > total biomass. I would appreciate to have a confirmation that the UTM
        > > coordinate system will account for the true shape of the Earth in my case
        > > and thus i could proceed to geostatistical modelling after transforming
        > > from latitude-longitude data to UTM. Thanks.
        > > Ruben
        > >
        > > --
        > > * To post a message to the list, send it to ai-geostats@...
        > > * As a general service to the users, please remember to post a summary of any useful responses to your questions.
        > > * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
        > > * Support to the list is provided at http://www.ai-geostats.org
        > >
        >
        > --
        > * To post a message to the list, send it to ai-geostats@...
        > * As a general service to the users, please remember to post a summary of any useful responses to your questions.
        > * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
        > * Support to the list is provided at http://www.ai-geostats.org
        >

        --
        Roger Bivand
        Econonic Geography Section, Department of Economics, Norwegian School of
        Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
        Norway, voice: +47-55959355, fax: +47-55959393; Roger.Bivand@...



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      • Jim Bash
        Sorry, I didn t notice the reference to the Faulklands, just the question about near the south pole . 60S isn t that near and UTM would be fine if the study
        Message 3 of 5 , Feb 14, 2004
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          Sorry, I didn't notice the reference to the Faulklands, just the question
          about "near the south pole". 60S isn't that 'near' and UTM would be fine
          if the study stays in one zone.

          On Sat, 14 Feb 2004, Roger Bivand wrote:
          > Hold on. hold on! Look, Bergen, Norway is 60N, the Falklands, even with
          > South Georgia, are not even 60S. I protest that this isn't that near the
          > poles, even the Arctic and Antarctic circles are at 66.6...N, and that's
          > well within the 80N/S of UTM. The question was whether to transform from
          > latlong to anything projected in order to do geostats, and the answer is
          > yes, unless your geostats software itself calculates great circle
          > distances from latlong coordinates (the fields package in R does, for
          > example). So the answer is yes, use a projection of choice, UTM being a
          > possibility (depending on the W-E extent of your data), or use software
          > that respects that your data are latlong.

          --
          * To post a message to the list, send it to ai-geostats@...
          * As a general service to the users, please remember to post a summary of any useful responses to your questions.
          * To unsubscribe, send an email to majordomo@... with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list
          * Support to the list is provided at http://www.ai-geostats.org
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