Monthly Archives: May 2008
By Aileen Buckley, Mapping Center Lead
This spring, we have caught up with many of you at a number of conferences. The presentations we gave at the conferences are now posted on the Other Resources page here on Mapping Center. Here’s a rundown of our latest activities… In April, we attended the Association of American Geographers meeting in Boston. There we gave a presentation on “Web Delivery of Cartographic Concepts and Best Practices”. Then we saw some of you at Carto 2008, jointly sponsored by the Canadian Cartographic Association and the Association of Canadian Map Libraries and Archives. At this meeting, held in Vancouver, BC, we presented an updated version of our “Evolution or Devolution of Cartographic Education” presentation and “Teaching Map Design using Mapping Center”. Most recently we attended Digital Mapping Techniques ’08 in Moscow, Idaho. There we gave a presentation on “Esri Cartographic Representations for the FGDC Digital Cartographic Standard for Geologic Map Symbolization”.
We really enjoy meeting with you at these events, and we look forward to seeing you at the UCGIS and other meetings in the near future!
There are many options to the GIS user when deciding what data store to use to store geographic data. At ArcGIS 9.2 we introduced a new type of geodatabase, the File Geodatabase. While all types of geodatabases have their strengths and weaknesses, we thought it would be useful to highlight some of the strengths of using this new type of geodatabase.
The database size is only limited by the available disk space. By default, individual tables and feature classes can be up to 1 TB. With the use of configuration keywords this can be expanded to 256 TB.
Works on many different operating systems including Windows and UNIX (Solaris and Linux)
Provides excellent performance and scalability. For example, to support individual datasets containing well over 300 million features and datasets that can scale beyond 500 GB per file with very fast performance. The file geodatabase out performs shapefiles for operations involving attributes, and scales the data size limits way beyond shapefile limits. Through the use of an efficient data structure that is optimized for performance and storage, File Geodatabases use about one third of the feature geometry storage required by shapefiles and Personal Geodatabases.
The File Geodatabase uses an edit model similar to shapefiles, supporting one editor and multiple readers. Each standalone feature class, table and feature dataset can be edited by different editors simultaneously but can only have one editor performing edits on them at any given time. This means that User A can edit the Roads Feature Class at the same time as User B edits the Parcels Feature Class.
File Geodatabases also allow users to compress feature classes and tables to a read-only format to reduce storage requirements even further. This reduces the Geodatabase’s overall foot-print on disk without reducing the performance.
By Charlie Frye, Esri Chief Cartographer
Have you ever wondered where a feature class came from as you’ve browsed over one of your geodatabases in ArcCatalog? I think most of us have, and probably more often than we’d like to admit. In the example shown here to the left, I made these datasets a few weeks ago, and I have no idea what “GN” means, and if or how I selected, simplified, or dissolved the data. Continue reading
Part II of a two part post on the GIS Education Community blog appeared the other day, picking up where the previous post left off with a discussion of how to take GPS readings and turn them into shapefiles, and then add hyperlinks.
But there’s another way to accomplish the same thing, and also new capabilities coming in ArcGIS Explorer 480 which will make things even easier.
One option might be to save the GPS coordinates as a comma or tab-delimited text file, and import the file to create results. We covered this topic in a post back in July, 2007, and while we were working with a much older version of Explorer at the time, the information in the post is still correct. A nice thing about results is that it’s very easy to do interesting things with their popups, which we covered in another post not long ago. So these methods could have been used instead of the shapefile creation method described in the Education Community post.
But soon there will be an even easier way. New in Explorer 480 is support for GPX format files. Wikipedia describes GPX as follows:
We visited the GPXchange site to download a file of interest, one with locations of hot springs in California. In the soon-to-be-released Explorer 480 we imported the GPX file and created a collection of waypoints from the downloaded file. We’ll save the step-by-step details for a later post, after we’ve released Explorer 480, but we ended up with a result group, with each result representing a waypoint in the file. Here we’ve clicked a couple of them to open the popup window to display more information about the waypoint.
We’re occasionally asked how to build a partial map cache at large scale levels, while having a full cache at smaller scales. This is useful if you have highly detailed data in certain areas of your map. For example, you might have medium resolution data covering the world and high resolution data covering just your country. How do you get the high resolution data in your cache without having to cache the full extent of the world at large scales?
Every map cache has a tiling scheme that defines the available scale levels. Think of your tiling scheme as an empty container of tiles. You don’t have to completely fill all scale levels in the tiling scheme; you can just partially fill the large scale levels. This post explains how to do that.
How does a tiling scheme get created?
The tiling scheme is represented by a file called conf.xml that is stored in your service’s cache folder in the server cache directory. (For example: c:arcgisserverarcgiscachemyCaliforniaServiceLayersconf.xml).
The way you get a tiling scheme is to run the Generate Map Server Cache tool. This tool creates a tiling scheme file from all the information you provided as tool input, such as the list of scale levels. After creating the tiling scheme, the tool also creates all tiles at all the scales you defined. If your goal is to create a partial cache, you need to stop the tool from creating all the tiles.
How can I create the tiling scheme without creating all the tiles
To get the tiling scheme without getting all the tiles, you can run Generate Map Server Cache and cancel it after about one minute. This won’t erase your tiling scheme; it will just stop the creation of tiles. If you’re nervous about whether one minute is long enough for conf.xml to get created, you can open Windows Explorer and verify that the completed conf.xml is in your cache folder before you cancel the tool.
So if I cancelled Generate Map Server Cache, how do I get tiles into my cache?
Even though you cancelled Generate Map Server Cache, you can still use Update Map Server Cache to add tiles to your cache. This tool isn’t just for updating existing caches; it is also very effective at creating new caches with a fine-grained level of control. You can tell the tool to cache only a subset of scale levels in your tiling scheme over a limited geographic extent.
You’ll need to run Update Map Server Cache several times in order to create your partial cache.
First, run the tool to Recreate All Tiles at small scales only, covering the full extent of the map document. This is the default extent that the tool uses.
The second time that you run the tool you can also choose Recreate All Tiles. But this time, select just the larger scales and give the tool a smaller rectangular extent. If you want to get real specific about which areas are cached at the large scales, you can script Update Map Server Cache to cover a series of rectangular extents. One example of this is Jeremy Bartley’s script that creates tiles based on the extents of features in a feature class.
Here’s a summary of the steps for building a partial cache:
- Run Generate Map Server Cache and cancel it after the tiling scheme file has been created (waiting about one minute should be enough).
- Run Update Map Server Cache on the full extent of your map for the small scales only.
- Run Update Map Server Cache again on a limited extent of your map for the large scales only.
- Optional: Configure your server to return a Data Not Available tile for empty cache areas.
A note about the road ahead…
We’re happy to announce that this workflow has improved in ArcGIS Server 9.3. The Generate Map Server Cache tool will be deprecated in order to separate the workflow of creating the tiling scheme and creating cache tiles. (Your existing scripts will continue to work.) You’ll also be able to create a subset of tiles based on the boundary of a feature class. Finally, you’ll have the option to cache areas on demand as they are visited by users. We plan many blog posts on these topics in the months ahead.
NASA’s PIGWAD (Planetary Interactive GIS-on-the-Web Analyzable Database) site offers a wealth of planetary information, including lots of information for Mars. PIGWAD’s mission statement from their Web site:
(1) Produce a web-based, user-friendly interface aimed at the planetary research community that will support Geographic Information Systems (GIS) graphical, statistical, and spatial tools for analyses of planetary data, including the distribution of planetary GIS tutorials, tools, programs, and information; (2) Create planetary GIS databases consisting of peer-reviewed digital geologic maps, feature maps, topography, and remote-sensing data under the scientific oversight of the NASA Geologic Mapping Subcommittee (GEMS); and (3) Support and encourage the use of GIS in planetary research including geospatial open standards.
What this means is that there’s lots of information for you to use with ArcGIS Explorer, both downloadable data in the form of shapefiles and rasters, as well as Web-based content services, and for a variety of planets and their moons.
Here’s one of PIGWAD’s ArcIMS-driven sites that allows you to view a variety of different information for Mars.
Though the content above is viewed in an ArcIMS Web application, we can also copy and paste the URL that we see in the address bar at the top of the app and create a connection directly from ArcGIS Explorer to the underlying ArcIMS services. To do that we had to do a little trial and error to determine the correct URL (PIGWAD doesn’t publish the direct connect information), but it was easy to determine. In Open Content we chose ArcIMS as our connection type to create, and typed the connection information shown below:
Once connected we can view the entire list of available services, and a good one to choose is Mars_general_image.
Once chosen we’re presented with a series of dialogs that allow us to choose specific sublayers, how they are displayed, and other parameters. You can accept the default for most of those, but there are two that we’ll take a closer look at.
The first is the dialog for choosing the Service Imagery Format. If you know the service is imagery-based, or global in context, select that option. If you know it’s vector-based, choose the vector option. For vector services that provide only partial coverage this is the best option since it will make transparent anything outside the data. For a more thorough discussion of the options, see the Imagery Format Help topic.
And here’s where we choose the specific sublayer(s) that we want. There’s a lot of them, and the easiest way to choose just one is to turn them all off with the topmost checkbox, then scroll down and choose just the sublayer we want. Here we’ve chosen the color shaded relief layer.
We can repeat these steps as many times as we like to access the specific sublayers we want to use in our Explorer map. See the Selecting IMS Layers Help topic for more details.
Since we’re technically still working with good old Planet Earth as our foundation, we also may want to remove things that aren’t appropriate for Mars. So we can turn off the positional text (Tools > Options > Map Display), atmospheric halo and fog (File > Map Properties > Environment) and also remove tasks and layers that don’t apply.
Here’s our completed map showing the use of the swipe tool. You can see we’ve turned ArcGIS Explorer into a “Mars Explorer.”
Though only given 50-50 odds, NASA’s Mars Phoenix Lander completed a successful touchdown just a short while ago, completing a remarkable 296-day, 422-million-mile journey. In celebration of the milestone, the first-ever landing near Mars’ north pole, we decided to have a closer look at the red planet using ArcGIS Explorer.
How’d we do this? We made use of some of the freely available content published on the Geography Network. Here’s how.
First we started ArcGIS Explorer and clicked File > Open to show the Open Content dialog. We choose Servers, and then clicked the button at the top to choose ArcIMS (all services on the Geography Network are currently published via ArcIMS). We typed in the connection information shown here:
For Geography Network services we don’t need a user name or password, so we just left those fields blank. Once you establish a connection to a server it will be saved in your list of connections, and you won’t have to enter this information again. Once connected you’ll see it open in the connection list.
Here we’ve scrolled down the list of available Geography Network services (there’s a lot to choose from) until we reached NASA Mars, then double-clicked it.
We also accepted the defaults for the dialogs that appeared after our selection, except for the IMS Layer visibility. ArcIMS services can contain many sublayers, and you can choose which ones you want to add. In this case we wanted to add the two sublayers in the Mars service as individual layers so we could control the label visibility independently of the Mars imagery. So we repeated this twice, once to add the Mars imagery, and a second time to add the place labels.
When we were finished, we had two new layers in our map that allowed us to create the mars scene at the top of this post.
By Aileen Buckley, Mapping Center Lead
An aspect-slope map simultaneously shows the aspect (direction) and degree (steepness) of slope for a terrain (or other continuous surface). Aspect categories are symbolized using hues (e.g., red, orange, yellow, etc.) and degree of slope classes are mapped with saturation (or brilliance of color) so that the steeper slopes are brighter. This will result in a map that has the colors shown to the right.
NOTE — This blog entry has been updated for ArcGIS 10.
The following post was written by Simon Woo, a product engineer on the geodatabase team specializing in Raster support in the geodatabase.
Previous versions of ArcGIS have provided various mosaicking workflows. We’ve tried to make the mosaicking experience better in each version, but have had varying feedback on performance, especially when outputting to a file format.
Prior to ArcGIS 9.3, the workflow to create a mosaic was to create a raster dataset and then use the Workspace to Raster Dataset tool to populate the new dataset.
In ArcGIS 9.3, we have provided a new workflow to make your mosaicking experience faster.
The new workflow is to:
- Create an unmanaged raster catalog with the Create Raster Catalog tool.
- Load all the raster datasets into the unmanaged raster catalog with the Raster to Geodatabase tool.
- Use the Raster Catalog to Raster Dataset tool to mosaic the datasets together.
From the tests that we have run, this new workflow is considerably faster. Below are a couple examples of comparison tests that have been run.
Mosaic Test 1
Here’s the test data we used:
Type of data: 3-band
Input format: TIFF
Number of files: 20
Average file size: 38.8 MB
Output format: TIFF
Using the old workflow of creating a raster dataset and then using the Workspace to Raster Dataset tool, this data took 1 hour and 35 minutes to mosaic.
Here are the steps with the new workflow:
First create an unmanaged raster catalog.
This creates an unmanaged raster catalog. Now load the data into the new unmanaged raster catalog:
Now use the Raster Catalog to Raster Dataset tool to mosaic the rasters in the unmanaged raster catalog into a single raster dataset.
We conducted a similar test using GRID data and it yielded the following results:
Mosaic Test 2
Type of data: single band data
Input format: GRID
Number of files: 60
Average file size: 5.7 MB
Output format: GRID
Old Workflow – 45 minutes
Create Raster Dataset time: 1 second
Workspace to Raster Dataset time: 45 minutes
New workflow – 4 minutes
Create Unmanaged Raster Catalog: 1 second
Raster to Geodatabase tool: 1 minute
Raster Catalog to Raster Dataset tool: 3 minutes
The new workflow is shown in model form in the following graphic:
Bookmarks are handy for navigating to a particular location that you want to visit often. Here’s a tip on how to create and manage your own collection of bookmarks using results.
First, remember that each result has a view property that you can set that enables you to click the result to zoom to a location/view of your choice. Just navigate to where you want to zoom, right click the result and open its properties. Choose Location > View.
Use the camera button to capture the view snapshot for the result, and save your changes. Now whenever you click on the result you will zoom to your specified view.
You can also set these properties for folders, and that’s how we’ll create a few bookmarks. Let’s create a collection of bookmarks that will take us to New York, London, and Redlands. Begin with an new folder by right clicking the result panel and choosing Add Folder.
The default name is “New Folder,” which we’ll want to change. Right click to open the context menu and choose Rename, or hover over the name and click to activate text entry, and change the name to Redlands.
Repeat these steps two more times, renaming the folders New York and London respectively. You should see something like this:
Now we’ll set the view for each of them, beginning with Redlands. Use the Find Place task or navigate to the view of your choice over Redlands. You can also tilt your view. When you’re happy with the view, open the properties for the Redlands folder.
Once the properties are opened, choose Location > View. You’ll see that we’ve not yet captured a view property, and the entry fields are blank.
You’ll also see the camera button in the upper right. To capture the current view, just click the button, then click OK.
Now whenever you click Redlands, you’ll zoom to the saved view. Repeat the steps for the New York and London bookmarks, and you’ll now have a collection of bookmarks that you can click to zoom to the desired location.
We can improve our bookmarks by creating another folder, renaming it, and dragging and dropping the bookmarks we created above into it. You should see something like this:
We can save these bookmarks with our map, or export the My Bookmarks folder to open again later, or share with others. Now you’re just a click away from any destination.
For more information on result properties, check the Results Window item properties Help topic.