LaudonTech's GIS Blog

I’ve never really liked using the scale values on a computer screen. The scale would depend on the dot size (DPI) of your screen. Imagine plugging your computer to a projecter. Then those values are really wrong.
Also remember that the scale continuously changes in the north/south direction because of the Mercator projection.

These values are dependent on the latitude at which you measure them and and assumed physical size of a pixel on your monitor. Numeric scale Google maps = Mass confusion. The dynamic scale bar Google uses is far the best way to communicate ground size.

I actually did a visual comparison of the Google Map on one monitor and an ESRI GIS map of the same area on the other monitor and recorded the scales. I understand they are not accurate, however, close enough for my purposes, er, at least around the 49th parallel.

Let me guess, you want to use that information in order to generate a tiling scheme for ArcGIS Server cache files (GenerateMapServerCacheTilingScheme)?! Have you been successful?

Not a bad idea…but I was actually just figuring out what reference scales to symbolize the data to for creating my own custom Google Maps tiles.

I would like to set my scale base on 1 mile view, 2 mile view, 3 mile views, will google let you create your own zoom level for example I want to create a zoom at 1:16,000

How about the width and height of the tiles per zoom level? And how do you determine the amount of rows and columns per zoom level? Anyone know?

I’ve made some calculations, and I do not reach the same scale values.
I use the tilling scheme provided by google to calculate envelope’s in each zoom level.
(Remember that Google Maps use Mercator meters)

Here are my results:

Zoom level 0 1:20088000.56607700 meters
Zoom level 1 1:10044000.28303850 meters
Zoom level 2 1:5022000.14151925 meters
Zoom level 3 1:2511000.07075963 meters
Zoom level 4 1:1255500.03537981 meters
Zoom level 5 1:627750.01768991 meters
Zoom level 6 1:313875.00884495 meters
Zoom level 7 1:156937.50442248 meters
Zoom level 8 1:78468.75221124 meters
Zoom level 9 1:39234.37610562 meters
Zoom level 10 1:19617.18805281 meters
Zoom level 11 1:9808.59402640 meters
Zoom level 12 1:4909.29701320 meters
Zoom level 13 1:2452.14850660 meters
Zoom level 14 1:1226.07425330 meters
Zoom level 15 1:613.03712665 meters
Zoom level 16 1:306.51856332 meters
Zoom level 17 1:153.25928166 meters
Zoom level 18 1:76.62964083 meters
Zoom level 19 1:38.31482042 meters

PS. you don’t have to know these scale values to create a tiling scheme for ArcGIS Server

[...] de 2x a 17x, a la verdad eso no se puede asociar a una escala fácilmente, ya algunos han hecho sus aproximaciones, llegando a buenos niveles de [...]

[...] de 2x a 17x, a la verdad eso no se puede asociar a una escala fácilmente, ya algunos han hecho sus aproximaciones, llegando a buenos niveles de [...]