Tag: scale

Strategies to Effectively Display Large Amounts of Data in Web Apps

ArcGISonline512

In the blog, “A Technical Approach to Large Feature Datasets”, we demonstrated methods to display large amounts of data quickly and without layer drawing errors. Although tools are available to draw a bazillion features quickly on the web, does showing … Continue reading

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First Python Add-in for ArcGIS for Maritime: Charting

Introduced with ArcGIS 10.1, Python Add-ins provide the newest mechanism for customizing an ArcGIS Desktop application (e.g., ArcMap). These add-ins take scripting to the next level by providing the ability to incorporate user interface elements (e.g., buttons, tools and toolbars) into the customization.  Continue reading

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Using scale visibility ranges for symbology in ArcGIS Online web maps

By Kenneth Field, Esri Research Cartographer

Using scale visibility ranges to set symbology in ArcGIS online web maps thumbnail

When creating a web map using ArcGIS.com Map Viewer, the basic approach involves adding operational overlays to a basemap.  As you add layers, they are set by default to be visible at all zoom scales. This often leads to problems at smaller scales as symbols overlap which can very easily render your map illegible and meaningless. By contrast, when you create a static map at a single scale you would consider the available map space and so design and position symbols to avoid these problems. It is useful to keep this principle in mind when designing web maps in a multi-scale environment since not all layers should necessarily be visible at all scales.  This blog entry shows you how you can use the visibility range settings in ArcGIS.com Map Viewer so that operational overlays are only visible at certain scales.  By taking a thoughtful approach to designing the content for your layers and setting their visibility range you can optimize the viewing experience for your map reader rather than bombard them with a mashup of tangled symbols. Continue reading

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Versatile New Maps: The Medium Scale Hydro Basemap and Hydro Reference Overlay

In the bad old days, you may have done some work for a client and got to a point where you just want to make a map for a meeting or a report.  One of the most time consuming parts of making a map from scratch was finding data for rivers, streams, and lakes, then turning each an appropriate blue, making each line the appropriate symbol, then symbolizing each stream segment.  It takes time to find a dataset that is good enough, at the right scale, and that looks good when you are done symbolizing everything.  It may take you hours to find the right data, symbolize, and label everything.

In my past life as a consultant, sometimes I had to start from scratch like this. I spent time finding and downloading appropriate scale data, checking it to see if it looks OK on my map, then symbolizing each stream and lake at least a little bit (most places I have worked don’t need glaciers symbolized) so they show up with the right symbol.  Once that is all set, I haven’t even started labeling each stream, which can take quite a while to get right.

Sometimes to save my clients money I would give up and use USGS DRGs, turning only the blue symbols on.  I often thought wouldn’t it be wonderful if there was some kind of national hydrologic map service on the internet that you can just add to your map and it just works?

Now there is… in the form of the esri Mapping Center Hydro Team Hydro Basemap.  We have made a medium scale hydro basemap of the United States, from 1:147,000 to 1:18,000.  And we think it will make a lot of things easier for our community.

The Hydro Basemap of the United States is based on NHD, but with a focus on analytical cartography.  These maps are made to show hydrologic networks connecting through a system.  What’s known as the ‘Hydro Basemap’ is just the Hydro Reference Overlay plus relief… At times you may have your own relief or basemap and may not need any background behind the rivers and lakes.  For that you don’t want the whole Hydro Basemap, just what’s called the Hydro Reference Overlay. That’s the only difference in the two concepts… the presence of relief.  These two products are close companions to one another.

Hydro Basemap

Gardiner, Maine area, esri Mapping Center Team Hydro Basemap of the United States

Actually the Mapping Center Team has gone way beyond the concept I described earlier.  What we actually built is a hydro basemap, but one that is ready for a multiscale experience.  You can take one of the applications we built such as the High Water Map, then recycle/repurpose the javascript application for your needs, and the basemap is ready for you to use.  Just add your data.

 Hydro Basemap mashup with USGS Gauges

A map created on arcgis.com using the hydro basemap, mashed up with the USGS river gauge service.

As you zoom in and out, streams turn on and off, and labels rearrange for you.  As you zoom in, more and more stream segments appear that are important to your map view.  As you zoom out, smaller streams that would clutter your map view are selected out of the cache and removed.  Streams do not turn off and on indiscriminately or based solely on size or flow, there is a sophisticated algorithm at work here that will prioritize small streams with big important names (such as the upper Mississippi River in Minnesota).  In addition, different parts of the country have different methods of stream prioritization, and these are respected.  There is no one size fits all method to pruning streams as scales change, since different parts of the country have different soils and drainage characteristics. Don’t worry, we have done this for you so you don’t have to.

It’s easy to get used to something like this because (as we like to think at the Mapping Center) it’s how things should have been all along. We at the Mapping Center Hydro Team are proud of this product and would like you to give it a spin, and see how you like it.  We’d like to hear your comment to know how easy this is for you to use.  I wish they had this when I was a consultant.

Special thanks to Michael Dangermond for providing this post. Questions for Michael:  mdangermond@esri.com

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John C Bartholomew award for small scale mapping

By Kenneth Field, Esri Research Cartographer

BCS award - thumbnail

Mapping Center Team member Kenneth Field recently received another award for his map ‘The Beautiful Game: A World of Football’. In addition to awards for the map at the 2010 Esri UC, Ken was presented with the John C. Bartholomew award for small-scale mapping at the recent British Cartographic Society Symposium in the UK. The coveted award is presented for originality and excellence in thematic (non-topographic, 1:100,000 and smaller) cartography. The award is made by Collins Maps, publishers of Collins and Times world atlases, and the family of the late John C. Bartholomew.

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DEM resolution, output map pixel density, and largest appropriate map scale

By Dr. A Jon Kimerling, Professor Emeritus, Oregon State University

DEM thumbnail

If you’ve used any raster DEM data to make maps you may have at one time or another asked yourself, “What is the appropriate map scale for the DEM I am using to make the map?” This question is tied closely to a basic principle of map compilation that you may have learned in your beginning cartography course: “Always compile your map from source materials of the same or larger map scales”. In our age of digital elevation models and other raster datasets, this basic principle of map compilation can be restated as: “Always create your raster map from data at the same or higher spatial resolution than the ground resolution of your map display grid cells”. The ground resolution of your map display grid cells will depend on the scale of your map. An equation you can use that relates map scale expressed as a representative fraction (1/x), DEM cell resolution, and map display resolution is:

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Crash Safety Templates Updated

Three new templates have been posted to our Roads & Highways Resource Center and are available in the Gallery!  Check out these analysis tools and web viewers.
The Crash Safety Analysis Template provides three industry standard tools – sliding scale, spot, and strip. These tools are now available in ArcGIS 10 as geoprocessing tools. The crash safety analysis tools can also be accessed through the web by using the Crash Safety Web Analysis Template. In this template the same geoprocessing tools are published with ArcGIS Server and consumed in this configurable Flex widget.
Our Crash Safety Dashboard Template has also been updated to the Flex 2.1 framework. This new framework allows for increased functionality as well as a more user friendly sample viewer layout.

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On map scale and raster resolution

By Rajinder Nagi, Esri Cartographic Product Engineer

Raster image

I am sure if you have used any imagery data to make maps then you have at one time or another asked yourself, “What resolution should the image be for me to be able to detect features in it?” Well, you don’t need to guess, because there is a mathematical relationship between the map scale and the image resolution.

In 1987, Waldo Tobler, renowned analytical cartographer (now emeritus from University of California-Santa Barbara) wrote, “The rule is: divide the denominator of the map scale by 1,000 to get the detectable size in meters. The resolution is one half of this amount.” Tobler goes on to note, “Of course the cartographer fudges. He makes things which are too small to detect much larger on the map because of their importance. But this cannot be done for everything so that most features less than resolution size get left off the map. This is why the spatial resolution is so critical.”

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