Jump to content

 
Photo

coordinate transformation

- - - - -

  • Please log in to reply
6 replies to this topic

#1
yeneneshabebe

yeneneshabebe

    Contributor

  • Validated Member
  • PipPip
  • 45 posts
  • Ethiopia

When a data is projected from one projection system to another projection system does the actual coordinate values of the data change? For example point data which show the extent of a town in Adindan projection system has the following values :

X Y
LL = 489000 1289000

UL= 489000 1294000

UR= 495000 1294000

LR= 495000 1289000

and the projected coordinate values in WGS 1984 projection system is identical with the Adindan. I used the project tool from Arc tool box. Is there another method for change of projection which results in different out put coordinate value?
In the project tool window Geographic transformation tab gives different options to transform from Adindan to WGS 1984 . I used Adindan_ To_WGS_1984_1. How can I know the appropriate one?

Any idea is valuable.

#2
frax

frax

    Hall of Fame

  • Associate Admin
  • PipPipPipPipPipPipPip
  • 2,308 posts
  • Gender:Male
  • Location:Stockholm, Sweden
  • Interests:music, hiking, friends, nature, photography, traveling. and maps!
  • Sweden

Hi - keep in mind that WGS84 is not really a projection - it is a datum/ellipsoid. We are sloppy, and we refer to the equirectangular (lat/long) projection (plate careƩ) with the WGS84 datum as "WGS84" (most often with decimal degrees).

I think you want a reprojection that gets you decimal degrees, don't you - and then those coordinates are totally wrong!
Hugo Ahlenius
Nordpil - custom maps and GIS
http://nordpil.com/
Twitter

#3
yeneneshabebe

yeneneshabebe

    Contributor

  • Validated Member
  • PipPip
  • 45 posts
  • Ethiopia

Hi - keep in mind that WGS84 is not really a projection - it is a datum/ellipsoid. We are sloppy, and we refer to the equirectangular (lat/long) projection (plate careƩ) with the WGS84 datum as "WGS84" (most often with decimal degrees).

I think you want a reprojection that gets you decimal degrees, don't you - and then those coordinates are totally wrong!


Thanks .

The coordinates are in meters. i.e

Projected Coordinate System: Adindan_UTM_Zone_37N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: 0.00000000
Central_Meridian: 39.00000000
Scale_Factor: 0.99960000
Latitude_Of_Origin: 0.00000000
Linear Unit: Meter

and what I want is to reproject to the following coordinate system:


Projected Coordinate System: WGS_1984_UTM_Zone_37N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: 0.00000000
Central_Meridian: 39.00000000
Scale_Factor: 0.99960000
Latitude_Of_Origin: 0.00000000
Linear Unit: Meter

I think now it is clear.

#4
Nick H

Nick H

    Legendary Contributor

  • Validated Member
  • PipPipPipPipPip
  • 307 posts
  • Gender:Male
  • Location:Caversham, Reading, England.
  • United Kingdom

Hi,

Do the coordinates below make sense for the points you gave? I've had a look at them in Google Earth and at least they appear to be in the right country, see:

http://confound.me.u.../EPSG_20138.kml


Lat/Lon
11.6614155674133 38.8990781900431
11.7066373053812 38.8990618237314
11.7066514126334 38.954118991064
11.6614296186927 38.954126430312

I used DNR Garmin (free) to perform the transformations from EPSG:20137 (Adindan_UTM_Zone_37N) to EPSG:4326 (WGS84), but I don't have a clue about how accurate they might be.

Regards, N.
Caversham, Reading, England.

#5
Hans van der Maarel

Hans van der Maarel

    CartoTalk Editor-in-Chief

  • Admin
  • PipPipPipPipPipPipPip
  • 3,881 posts
  • Gender:Male
  • Location:The Netherlands
  • Interests:Cartography, GIS, history, popular science, music.
  • Netherlands

The coordinates are in meters. i.e

Projected Coordinate System: Adindan_UTM_Zone_37N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: 0.00000000
Central_Meridian: 39.00000000
Scale_Factor: 0.99960000
Latitude_Of_Origin: 0.00000000
Linear Unit: Meter

and what I want is to reproject to the following coordinate system:


Projected Coordinate System: WGS_1984_UTM_Zone_37N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: 0.00000000
Central_Meridian: 39.00000000
Scale_Factor: 0.99960000
Latitude_Of_Origin: 0.00000000
Linear Unit: Meter

I think now it is clear.


The second one is exactly the same as the first one, except for the name. So I'm guessing it's just referring to the fact that it's using the WGS84 ellipsoid as a base for a UTM zone 37N projection, rather than a Plate Carree on WGS84. Like Hugo said, there does seem to be a great deal of confusion with these names and "WGS84" can mean different things.
Hans van der Maarel - Cartotalk Editor
Red Geographics
Email: hans@redgeographics.com / Twitter: @redgeographics

#6
yeneneshabebe

yeneneshabebe

    Contributor

  • Validated Member
  • PipPip
  • 45 posts
  • Ethiopia

The coordinates are in meters. i.e

Projected Coordinate System: Adindan_UTM_Zone_37N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: 0.00000000
Central_Meridian: 39.00000000
Scale_Factor: 0.99960000
Latitude_Of_Origin: 0.00000000
Linear Unit: Meter

and what I want is to reproject to the following coordinate system:


Projected Coordinate System: WGS_1984_UTM_Zone_37N
Projection: Transverse_Mercator
False_Easting: 500000.00000000
False_Northing: 0.00000000
Central_Meridian: 39.00000000
Scale_Factor: 0.99960000
Latitude_Of_Origin: 0.00000000
Linear Unit: Meter

I think now it is clear.


The second one is exactly the same as the first one, except for the name. So I'm guessing it's just referring to the fact that it's using the WGS84 ellipsoid as a base for a UTM zone 37N projection, rather than a Plate Carree on WGS84. Like Hugo said, there does seem to be a great deal of confusion with these names and "WGS84" can mean different things.


Thank you Hans! what I want is a projected coordinate system in WGS 1984 for these given points in local datum i.e Adindan. The conversion is required to purchase a high resolution satellite image for the town and the image providers want a global coordinate system (WGS 1984 projected) i.e the unit of measurment is in meters . So could u help me on this. Thanks in advance.

#7
yeneneshabebe

yeneneshabebe

    Contributor

  • Validated Member
  • PipPip
  • 45 posts
  • Ethiopia

Hi,

Do the coordinates below make sense for the points you gave? I've had a look at them in Google Earth and at least they appear to be in the right country, see:

http://confound.me.u.../EPSG_20138.kml


Lat/Lon
11.6614155674133 38.8990781900431
11.7066373053812 38.8990618237314
11.7066514126334 38.954118991064
11.6614296186927 38.954126430312

I used DNR Garmin (free) to perform the transformations from EPSG:20137 (Adindan_UTM_Zone_37N) to EPSG:4326 (WGS84), but I don't have a clue about how accurate they might be.

Regards, N.


Thnk you Nick! what I want is a projected coordinate system in WGS 1984 for these given points in local datum i.e Adindan. The conversion is required to purchase a high resolution satellite image for the town and the image providers want a global coordinate system (WGS 1984 projected) i.e the unit of measurment is in meters . So could u help me on this. Thanks in advance.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

-->