3 replies to this topic

[stebbo]

Hi,

Say you've got a google satellite map and you know the lat/long of one point of the map, as well as the scale of the map and its bearing. Can anyone please point me to the right direction to calculate the lat/long of other points on that map?

Edited by stebbo, 07 April 2008 - 12:21 AM.

[bebe onea]

Hi,

Say you've got a google satellite map and you know the lat/long of one point of the map, as well as the scale of the map and its bearing. Can anyone please point me to the right direction to calculate the lat/long of other points on that map?

If the satellite map is georeferenced open it in any GIS software ( Global Mapper, etc.) and you will find the coordinates of any point you want by pointing at it with your cursor.

[stebbo]

If the satellite map is georeferenced open it in any GIS software ( Global Mapper, etc.) and you will find the coordinates of any point you want by pointing at it with your cursor.

No, unfortunately it's not georeferenced. I've decided to just to work out how many lateral and longitudinal degrees are represented per metre at this location, and hopefully this, especially longitudinal variation / metre doesn't give too much error.

Thanks.

[mdsumner]

If the satellite map is georeferenced open it in any GIS software ( Global Mapper, etc.) and you will find the coordinates of any point you want by pointing at it with your cursor.

No, unfortunately it's not georeferenced. I've decided to just to work out how many lateral and longitudinal degrees are represented per metre at this location, and hopefully this, especially longitudinal variation / metre doesn't give too much error.

Thanks.

You only need 2 points on the image, with 4 unique coordinate values: convert those coordinates to the projection of the image (if they are not already), then work out the pixel size (how many pixels per coordinate unit?) and from that the position of one of the image corners. Then you have enough to georeference it.