1

At the same zoom level, the scale bar of a map from Google Maps API (v3) can have different sizes. Here are two screenshots I took at the same zoom level on the same map at two different locations.

Indianapolis enter image description here

Cambridge (UK) enter image description here

You can try it yourself on this page (go to the second map, the one with the scale bar). http://tech.reumer.net/Google-Maps/Demo-Google-Maps-V3/show-all.html

In my application, I have two maps and I want these maps to always have the same scale. I started out by forcing them to be at the same zoom level (with some js listeners), but it looks like it's not going to be enough.

Is there a way to force same scale maps or a specific scale (as opposed to a specific zoom level) on Google Maps API? Which competitors offer this feature?

3

The locations you specify are at different latitudes. Because the Spherical Mercator implementation used by Google maps compresses latitude, the scale will change depending on the distance from the Equator.

In your example, try zooming out a long way, then navigate northwards. You'll see that the scale bar gets progressively longer as you pan.

  • Dammit. I dreaded this answer. Is there a way to fix the scale bars to be of a specific length and to adjust zoom consequently? My goal is two have 2 maps of different locations in the world on which I can compare distances… – cpa Jul 25 '14 at 2:17
  • @cpa: No you can't vary the zoom. The zoom levels are fixed, and even in one tile, the scale will not be uniform in different directions. – Devdatta Tengshe Jul 25 '14 at 2:50
  • I understand it's not uniform but for the scale my app will be used at, it doesn't really matter. Are there any competitors which would let vary the zoom? – cpa Jul 25 '14 at 12:39
1

Theoretically, you could build a map cache (series of rectangular map tiles stored as graphics files (png, jpg, etc) using an Equidistant map projection, and only need one scale bar per zoom level anywhere in the world. However, people might not like the way it looks, and it may not preserve direction (i.e. north being always "up", etc) which may wreak havoc on the navigation part of google maps. Alternatively, you could use a spherical map viewer, like Google Earth Pro, to take measurements and keep the size of the scale bar the same at any given zoom level, since you are not using a flat projection there.

-2

There's no reason the scale can't be lined up, latitude or not. If I take a screenshot of one map, I can use MS Paint to resize it until it's the same scale as a second map, therefore Google could do the same.

  • Can someone please explain why this has been marked down? surely if I adjust image 2 until the scale bar is the size of image one I am not ruining the integrity of the scale bar? What am I missing? – David Sigley Jan 11 '15 at 17:55

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