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Google Maps: Add the Contour Interval to the Legend of your Terrain maps
|| 8/6/2009 || 3:56 pm || 5 Comments Rendered || ||

Nearly every printed topographic map I’ve ever looked at has the contour interval, otherwise known as the distance between contour lines, listed in the legend. Depending on the scale of the map, the contour interval ranges from 1 foot to hundreds of feet between each successive contour line. The contour interval allows the map reader to instantly know the relative steepness & flatness of the topography in the map at one quick glance. Because of this crucial information, a topographic map is considered incomplete when it does not disclose this information to the reader.

Enter the Terrain feature of Google Maps. Released to the public in November of 2007, the contour lines were subsequently added in April of 2008. I hadn’t really given the feature much use until last week when I was planning my weekend excursion to the Shenandoah mountains. I was trying to figure out the altitude variation on my friends property by finding where their property line started & ended and calculating the elevation change. Since their property lies on the side of a mountain, I wanted to know the altitude at the bottom of the property and the altitude of the highest portion of the property, and subtract the difference to find the total elevation variance.

What I found out instead was that Terrain function of Google Maps was lacking the contour interval declaration in the legend. As with all their maps, the lower left-hand corner showed the units of distance on the map, but was missing the topographical information provided by the contour interval declaration.

In lieu of ever getting a response from Google Maps after previous queries, I decided to send a tweet to Google Maps:

Screen grab of my tweet to Google Maps

I wasn’t really expecting a response, but a couple hours later I received this response on Twitter:

Screen grab of Google Maps response to my tweet

Well duh. I knew that! But that is not how a topographic, err, Terrain map should operate. The user should not have to zoom all the way in, count the number of contour lines between the bold contour lines, and figure out the difference. This information should be visually presented to the user in the legend, just like how the spatial distance is shown. This is not about dumbing down the maps for users, rather, its about offering users a complete map that includes all the basic information that should be there in the first place. I responded to their tweet:

Screen grab of my tweet to Google Maps

I still have yet to receive a reply…. So I have gone one step further and made some mock-up maps of how the contour interval declaration might look like.

Unlike the Satellite (and Aerial!) option on Google Maps, which allows users to zoom in as far as the imagery allows before pixillation (which is contingent on the spatial resolution of the aerial & satellite imagery), the Terrain feature has fewer zoom in levels for users to navigate. If you look closely at a URL from Google Maps, somewhere in the URL you’ll find “z=X,” where z equals Zoom (scale), and X relates to how close to the surface of the earth the map show, where a z=5 is far away and z=15 is close to the surface. The Terrain feature only shows the contour lines at 3 scales, x=13, x=14, and x=15, which means there does not need to be a complete overhaul of the Terrain maps.

Below are six Google Maps of the Continental Divide in Rocky Mountain National Park showing three different scales and how the contour interval could be shown on the maps. Of note, I am not using the bold contours as the interval, but the individual contour lines. I was able to figure out the contour interval by counting the number of intervals (5) between the bold contour lines and dividing the difference from the elevation listed on the bold contour lines.

:: Terrain Map at Z=13 ::
Google Map of the Continental Divide in Rocky Mountain National Park at z=13

:: Terrain Map at Z=13 with the contour interval declaration at the bottom ::
Google Map of the Continental Divide in Rocky Mountain National Park at z=13 with contour interval declaration

I found this map to be the hardest to decipher the contour interval because the individual contour lines are so lightly drawn

Continue Reading:

:: Terrain Map at Z=14 ::
Google Map of the Continental Divide in Rocky Mountain National Park at z=13

:: Terrain Map at Z=14 with the contour interval declaration at the bottom ::
Google Map of the Continental Divide in Rocky Mountain National Park at z=14 with contour interval declaration

:: Terrain Map at Z=15 ::
Google Map of the Continental Divide in Rocky Mountain National Park at z=15

:: Terrain Map at Z=15 with the contour interval declaration at the bottom ::
Google Map of the Continental Divide in Rocky Mountain National Park at z=15 with contour interval declaration

While my use of the Geneva font with a 2 pixel white stroke might not look the best on these maps, I believe that the interface designers & programmers at Google Maps can easily implement this basic information to the legend of their Terrain maps. Yes, there will be a minor difference in the contour intervals on the maps that use meters instead of feet, but overall I don’t think it will make a large difference. The real issue is still providing users with the best & most useful maps on the internet, and until Google Maps includes this basic information, their maps will still be cartographically incomplete. The question is, will the maps be updated?

Post Title: Google Maps: Add the Contour Interval to the Legend of your Terrain maps
Post Tags: , , , , , , , , ,
Posted in: Cartography, Colorado, Commentary, Google Maps, Location, Twitter
Last edited by Nikolas Schiller on 8/27/2009 at 1:09 am

  1. I grew up in the U.K. reading maps–notably the excellent Ordnance Survey maps. I don’t care one bit about 3D in terrain view IF and ONLY IF the contour lines are present and the intervals are labelled. I notice that the interval oin Google terrain maps varies depending on where you are in the US. I needed to know the height of a place in Georgia, and it took way longer than it should have to find labelled contour lines and to figure out that the interval was 40 feet. A simple key would have given me the answer I needed right away. IMHO instruction in geography in this country is sadly lacking.

    Comment by Trish J — 8/14/2009 @ 7:45 pm

  2. I agree 100%!! Maybe Google will fix this. I hope they do.

    As for instruction in geography— I think most Americans get very little geography taught in school. If I had a dollar for every time a friend couldn’t place my home town of Saint Louis on a map, I’d be a wealthy man.

    Comment by Nikolas Schiller — 8/14/2009 @ 7:53 pm

  3. Sure, this works great on really hilly terrain.
    I life in relatively flat Rhode Island, and all I see is a 200ft bold contour and a bunch of unlabeled other lines. What the heck is the interval between the unmarked lines?? Is everything between sea level and 400ft?

    It may seem flat overall, but it sure would be nice to know what you’re getting into when climbing out of the valley on a bicycle!


    Comment by E — 8/27/2009 @ 2:23 pm

  4. I completely agree with ‘E’, post # 3. I fly radio control slope sailplanes in the Midwestern US, and some known slope soaring hills have only one bold contour line and two or three light contour lines, so there doesn’t seem to be any way to calculate the interval between them.

    By the way, regarding education in the U.S., we have a conservative political party that wants to keep the citizens ignorant and incapable of logical thinking.

    Also, the curriculum of our primary and secondary school textbooks is largely determined by the Texas Board of Education, which has been captured by a group of Fundamentalist Christians who believe that the Genesis story is at least as valid a theory as evolution, that the separation of church and state is a fiction, that George Washington, Thomas Jefferson and other prominent founders of the U.S. were Christians, not Deist, and that America is a Christian nation.

    I wish I could move to France.

    Comment by Jeff Thompson — 3/24/2010 @ 12:19 pm

  5. I agree 100%.

    Topographic curves probably are the most useful item of information on maps, provided YOU are in control.

    I need to figure out what parts of the Bolivian amazon will be flooded when rivers rise by 1,2,3… feet, in a given area.

    That is what topography is for (among many other important uses).

    Please, give us the tools for that kind of analysis. You do have the altitude of each pixel (more or less). So all you need is the software and the GUI.

    Thanks in advance, that would be so useful!!!

    Rodrigo CABALLERO

    Comment by Rodrigo CABALLERO — 6/7/2010 @ 10:27 pm

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