[OSM-talk] [Talk-in] Coastline changes at different zoom withyahoo map

David Groom reviews at pacific-rim.net
Fri Aug 22 17:51:16 BST 2008


Shajeer


There does seem to be a bit offset between the low resolution and high satellite images used on the Yahoo layer.

It would appear that after the import of coastline data from the PGS script,(which gave a coastline approximately following the low res imagery) the coastline way  has been manually adjusted to fit the higher resolution imagery.

Without some form of independent verification of position using GPS tracks its difficult to ascertain which is the more correct. Though my guess is that the PGS import which tied up to the low res Yahoo imagery is probably the more correct as 2  independent sources seem to be in agreement.  Unless Yahoo use staring landsat images without doing their own rectification in which case I guess these might not be 2 independent sources
 
I've not noticed this sort of offset anywhere else

David
  ----- Original Message ----- 
  From: Mikel Maron 
  To: talk-in at openstreetmap.org ; talk at openstreetmap.org 
  Sent: Friday, August 22, 2008 5:13 PM
  Subject: Re: [OSM-talk] [Talk-in] Coastline changes at different zoom withyahoo map


  There's possibly inaccuracies  in the original coastlines. 
  I'd suggest reading about how coastlines are handled (http://wiki.openstreetmap.org/index.php/Coastline)
  and then making an inquiry to the main dev at openstreetmap.org list.

  -Mikel



  ----- Original Message ----
  From: Shajeer Mohammed <shajeer at hotmail.com>
  To: talk-in at openstreetmap.org; talk at openstreetmap.org
  Sent: Thursday, August 21, 2008 10:50:03 PM
  Subject: [Talk-in] Coastline changes at different zoom with yahoo map

  I haven noticed the same coastline when compared at different zoom levels 
  are having an offset when compared to the yahoo satellite maps.


  http://www.openstreetmap.org/edit?lat=11.85657&lon=75.35504&zoom=15 - 
  Modified coastline which shows the city roads and coastlines aligned
  http://www.openstreetmap.org/edit?lat=11.85657&lon=75.35504&zoom=13- Orginal 
  PSG coastline my changes are shown with an offeset

  Has anyone else noticed this? Or am I doing something wrong here?


  Regards
  Shajeer





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