blankblank blank

Archive for the 'GIS' Category Page 2 of 23

ShareGeo: Open Geo Data Repository

Addy Pope of the University of Edinburgh writes to announce ShareGeo, a data repository for open geo data that is freely shareable and distributable. While it’s open for use by anyone, the datasets currently available show a not-surprising bias towardsUK-related data. You can search for data by date, subject, source, title, or more generally by defining geographic extents:


The initial view shows the defined area of interest as the yellow rectangle; you can adjust the extents by modifying the lat/long coordinates directly, or drag/drop the green markers to redefine the extents directly:


Once done, click on Search, and get both a list of available datasets for that area:


And a map that shows the extents of all datasets listed below it:


Click on a maker to identify which dataset’s extents it corresponds to. If you move to another page of results, this map will update automatically to show the extents of the new results listing.

Registered users (free) can upload data directly to the repository, or use a free extension to upload directly from ArcGIS.

Free Geographic Datasets From WeoGeo

Weogeo is a paid geographic data service that lets you create an online library of geographic data files, and share them with one or more users (free 30-day trial subscription available for the library, if you want to try it out). It also has a market side, that lets you put datasets up for sale online, and handles the financial transaction part. But they’ve also been putting a number of free datasets up on the market site, available for anyone to download (with free registration).

WeoGeo’s Fiducial Marks blog has been posting updates on free datasets on a regular basis. For example, the most recent being the NGIA’s Geonet Name Server,  a free database that “has accumulated over 5 million features with 7 million feature names.  It contains a name for every geopolitical area (country) in the world, including various land features”. The original dataset is in text format, and weogeo has converted it to shapefile format for more convenient use in a GIS. If you’re already registered on the site, the direct link at the blog post will take you to that dataset. But you can also browse/search the other datasets available at the site. After registering, go to the Market page and click on “Start Now”.


Select the general area you’re interested in with the pane at left; enter coordinates, city/country/zip code, or drag the selection box to the desired area. The selected area will be actively updated in the Refine box at right; you can also zoom in/out in Refine, or drag the map to move it to a different area, and have the changes reflected on the left. Next always moves you on to the next step.


The Browse pane shows all datasets that contain any data that lies within the defined geographic area. As you zoom in on the map at left to select a smaller area, this list can actively shrink as datasets outside the selected area are dropped. By default, all vector datasets for an area are displayed. To search for specific datasets, or change the data type to raster, click on the Advanced Filter tab at the bottom.


Data options are Vector, Raster, Data Types (both vector and raster), and Other. You can also refine the data types by searching by rating, cost, and text terms (no Booleans in text search, as far as I could tell). To search for free datasets only, just move the right cost slider all the way over to the left.


One note on raster data searches. weogeo has all USGS topographic maps (1:24K) available for download, but if you’re zoomed out even a small degree, you’ll get dozens if not hundreds of maps listed in the data browser. Zoom in as close as possible to your target area to reduce the size of this list. In the view above, the darker shaded areas represent the maps listed at right; click on a map listing at right, and it will be highlighted/darkened at left.


The next two panes provide a preview of the map, and then additional options, including file format (GeoTiff default for topos, but you have the option for others including JPG, ERDAS IMG, and ESRI HD; you can also choose the datum of the output coordinate system (NAD27, NAD83 or WGS84 here).  When ready, click on Order:


Make sure you check the “Accept Content License” box (and check the Total Charge, to make sure you haven’t chosen a paid dataset in error). Click on Order Now, and in a short period of time, you’ll get an email with a link to the download page for your data.


You have two options for downloading the data. weogeo’s preferred method is to use their WeoApp (Windows/Mac/Linux), which manages not only downloads but also uploads if you have a library account. Clicking on the Via WeoApp link will download a .weo file, which you then open with the WeoApp to download the data into a destination folder. Clicking on Via Web takes you to a page with a download link to the data in zipped file format.

They may not have the exact dataset you want, but it’s definitely worth a visit just to check out what they have; much of it looks like it could useful at some point. And keep monitoring the Fiducial Marks blog to see what new datasets get added.

Useful ArcGIS Explorer Add-Ins III

One final set of add-ins for the excellent GIS data viewer ArcGIS Explorer, discovered by searching the site (since there doesn’t seem to be a gallery/catalog section for these on the site). Here’s the link to Part I, and here’s Part II.

Table Viewer – Supposedly adds the ability to view tabular database data, a feature sorely missing from the default installation. But I tried to figure out how to open a shapefile’s DBF table (supposedly supported by this option) without success; maybe you’ll have better luck. Also supposedly supports online geodatabases.

Query FeaturesExplorer has a built-in Query function (available on the Tools tab) that creates a classic SQL query, and then highlights all matching features in the map view:


The Query Features add-in works somewhat differently – it creates a tabular view of matching features, and then clicking on a table entry zooms you in to that single feature on the map:


You can use both query functions at the same time, and they complement each other quite well.

AGX2KML – Takes the current map view, and converts it into a KMZ image overlay file for use in Google Earth. Here’s a queried selection for the Jurassic Morrison format in Arizona, viewed in Explorer and then converted to a KMZ overlay:


PhotoOverlay – Lets you create a KMZ overlay from an input image. Bit clunky to use, as it requires you to enter the N/S latitude and E/W longitude limits for the image manually, or by clicking on the map; would work better if you could georeference any points on the map image to points in Explorer; as is, you’d probably be better off loading the image directly into Google Earth and manually calibrating the image.


PhotoPoint – A utility to simplify (somewhat) the adding of picture data to a map. In the main add-in input window, you specify the picture (either URL or local file), and add additional descriptive data; you can specify coordinates by clicking on the map, or typing them into the box.


This utility does not recognize embedded geotagging data, nor will it embed coordinate data into the photo; it just creates a photo content file on the map, with a pop-up that includes the entered data:


If you want to geotag images, or use geotagged photos, the Image Geotagger add-in (described here) might be a better choice; no popup text data entry options, but it will use embedded geotagging data to place the photo.

Finally, there are some expansion packs that add additional capabilities to ArcGIS Explorer; links to the downloads can be found on the main ArcGIS Explorer Desktop download page.

Projection Engine Expansion Pack – The default install of ArcGIS Explorer Desktop comes with geographic coordinates as the default (lat/long/WGS84); in the Display section, you can select MGRS or USNG grid directly from the Coordinates dropdown, or choose “More” to get a full list of available coordinate systems. The Projection Engine Pack adds some more coordinate systems to this “More” section.

Fonts Expansion PackLike it says, makes more font choices available for labels.

Data Access Expansion Pack – “Expands geodatabase functionality by allowing direct connections to multi-user geodatabases.” No personal experience with this.

Useful ArcGIS Explorer Desktop Add-Ins II

Continued from Part I yesterday …

GeoNames Find – Enter the name of a geographic feature, and ArcGIS Explorer will go the best fit for the entered name, as well as offering a full set of options.


Find GNIS Features – Select a US state/county, and a feature type from the Geographic Names Information System (GNIS), like town, arch, summit, mine, reservoir, etc., and get all such features in that area plotted:


Double-click on any of the names listed, and the map will zoom in on the selected feature:


Panoramio – Pan/zoom to your desired area, and get photos from Panoramio:


Photo thumbnails will be plotted on the map; double-click on a thumbnail to get a larger-sized image in a pop-up:


Wikipedia – Same general idea as Panoramio; go to the desired area, and search for Wikipedia entries geotagged to that location (or search by text):


Entries will be plotted on the map; double-click on a “W” icon to get the start of the Wikipedia entry, and a link to go to the full article:


Set Transparent Color For Image Overlay – Image overlays are graphics that sit at a constant spot in the view; examples might be a logo graphic or map legend. This add-in lets you set a transparent color, useful if you have a logo/legend on a white background, and you want the background to disappear. Unlike the map transparency feature, this will work with graphics with indexed colors (TIFFs, GIF, PNG).

Drive Time Analysis – An interesting example of the kinds of analysis tools that can be created using the ArcGIS Explorer SDK. This add-in calculates areas within a certain driving time of a user-specified starting point (up to 15 minutes driving time in this sample add-in). Below, the lightest color is 5 minutes, next is 10, darkest color is 15 minutes away.


Still a few left; I’ll save those for Part III.

Useful ArcGIS Explorer Add-Ins I

Yesterday’s post was about the latest version of ArcGIS Explorer Desktop, ESRI’s digital globe and GIS data viewer. One of its major advantages over Google Earth is the ability to create “add-ins”, user-programmable plug-ins that add functionality. But there doesn’t seem to be a catalog/gallery of these add-ins at the ArcGIS site. Searching around, I found a bunch of potentially useful ones. Install them by downloading the “eaz” file, then go to the Display ribbong, Options section, click on the Resources link, select “Manage Add-Ins”, and choose the downloaded eaz file. Add-ins will show up either on the Add-Ins ribbon, or in some cases in the Analysis section of the Home ribbon.

Garmin Tools – Converts an ArcGIS display into a KMZ overlay file compatible with newer Garmin units; there was a post on this tool a while back on this site.

Georeferencing – Import a raster image, and then georeference it using a three-point affine transformation. Works well with Mercator-based map projections. Limited support for some raster formats (e.g. doesn’t work with indexed-color TIFF files), and parts of the image can disappear after georeferencing. Finally, you can’t export the georeferenced image, though you can save it as part of the default view in ArcGIS Explorer. Addendum: Whoops – just found a world file and XML file that go with the image file. However, the world file is in geographic coordinates regardless of what the original image’s projection is in; it also includes non-zero rotation parameters, which a fair number of GIS programs can’t handle.

Capture Presentation Slides, Convert Presentation to PPT – Explorer Desktop lets you create presentations from map views. “Capture Presentation Slides” automatically creates a basic presentation by zooming in to every data layer loaded, creating a title from the data name, then generating a slide. “Convert Presentation to PPT” captures the slides as JPGs, then creates a PowerPoint file to display them.

Visibility Analysis – Generate a viewshed from a chosen point using 90m DEM data (maximum distance is 20 km), which is added to the data layers.


Image Geotagger – Add a previously-geotagged image, or geotag a new image and have it saved under a different name.


The image will show as a small thumbnail on the map; click on it to bring up a pop-up window with a full-scale view of the picture.

Terrain Profile – Draw a single track line, or series of track line segments, and get an elevation profile along that track.


Bing Birds Eye View – Click on the map, and get a pop-up with a Bing Maps window; not just Birds Eye oblique views, but the option for standard Bing Maps as well.


Street Viewer – Similar to the above, but brings up a pop-up window with the Google Street View display (and interactive viewer)


More tomorrow …

Hey, ArcGIS Explorer Desktop Has Turned Out Pretty Good!

Yeah, that’s not news to a lot of you, but it is to me. My last significant exposure to ESRI’s ArcGIS Explorer digital globe software (Windows only) was back when it came out, quite a few years ago. I tried it, and found it inferior to Google Earth in performance in 3D, and too complicated to bother learning it; since then, I’ve stuck strictly with Google Earth. A recent post on the free Garmin Tool application, which creates Garmin Custom Map overlays using ArcGIS Explorer, forced me to look at it again, and I was surprised to discover that it’s turned into a pretty cool, and pretty useful tool. Not perfect – the 3D performance is still pretty weak compared to Google Earth, and the out-of-the-box configuration isn’t as strong. But it has it’s own very strong set of features, and when used in 2D mode, is a good addition to any geography toolbox. Nice re-organization of tools/features in a MS-Word-like ribbon format, much better than the original interface.

  • A good selection of basemap imagery sets, including Bing Maps (aerial/road/hybrid), general world imagery/topographic/road maps, OSM, general terrain shading and National Geographic shaded topo maps:


No vector basemap data, like the roads you’ll find in Google Earth.

  • Add raster/vector data from multiple data sources and types: ArcGIS Online, GIS web services (ArcGIS servers, GeoRSS, WMS), ArcGIS lyr files, shapefiles, KML, GeoDatabases, text files, georeferenced raster imagery (e.g. GeoTiffs), and GPS data files (GPX).
  • Vector editing tools: Point, Line Area, Circle, Rectangle.
  • Export data in KML format (for user-created vector data), nmc map content packages for other ArcGIS Explorer users, or lpk layer files for ArcGIS.
  • Driving directions/routing
  • Add links to non-geographic data (documents, images)
  • Measurement tools for distance/area
  • Create a slide presentation by saving a series of map views
  • Time/flight animations

Oh the “needs work” side:

  • In the default install, I can’t find a way to set shapefile colors/sizes/symbols to depend on attribute values. For example, if you have an area shapefile with multiple subareas, each depicting an area with a separate property, they’re all displayed with the same color. For a GIS data viewer, this is a major missing feature. No selection/filtering by attribute either. The only way to view attribute data is through an on-screen pop-up; no tabular views of the DBF data.
  • I initially thought there was no adjustable transparency for raster/vector layers, but it’s under the Appearance ribbon tab, instead of in the Properties window for each layer, which is where you’d normally expect to find it.
  • Zoom and tilt controls are the opposite of every other digital globe I’ve used; scroll the mouse wheel away from you to zoom in, click the center button and move the mouse away from you to tilt the view to an oblique angle. And boy, can it be unresponsive sometimes in 3D mode! I usually only use the program in 2D mode only, so as not to have to deal with those issues.
  • There’s a nice interface for querying/previewing datasets available in ArcGIS Online, but there’s no comparable gallery of pre-packaged content files (NMC/NMF files) anywhere on the ArcGIS website, at least that I could find.
  • The app comes with the ability to add GIS-like analysis tools, as well as utilities like the Garmin Tool mentioned above (created with .Net and a free SDK kit from ESRI). By default, it comes with a buffer tool only; the process for adding additional tools isn’t explained very clearly in the help file. And while there’s a fair number of tools available, they’re hard to find; there doesn’t seem to be any systematic directory or catalog of them on the ArcGIS site. With some work, I tracked down some of them, and will post on them tomorrow.

Free GIS Data Acquisition And DisplayTool For The iPad

Don’t have an iPad, and my head is thoroughly into Android, so when I got a comment informing me about Corvallis Microtechnology’s new free iPad application iCMTGIS (iTunes link here), I almost ignored it. Big mistake – this looks like a pretty sweet field GIS data acquisition tool for the iPad!

  • Point, line and area data acquisition, either by GPS, manual entry, or distance/angle value entry
  • Full attribute entry capabilities, including setting up hierarchical data entry forms
  • Attribute query on-screen
  • Multiple data layers
  • Measure/calculate distances and area
  • Use aerial imagery as backgrounds
  • Import shapefile data
  • Export data in shapefile format, or PMP format for use with Corvallis Microtechnology’s own proprietary GIS programs

A few screen captures from their PDF brochure:




May not have all the features of an ArcPad or TerraSync, but this sure looks a  hell of a lot easier to use! Almost makes me wish I had an iPad to try it out on; if you give it a spin, leave a note in the Comments section. I have to hope and believe that similar apps will make it on the Android platform in the not-too-distant future.

A Terrible “Review” Of Free GIS Options

Open-source advocates can sometimes be a bit sensitive of criticism of open-source software. And they can sometimes overstate the benefits of open-source over closed-source programs, either free or paid. I use lots of open-source software, and am glad it’s there, but recognize that closed source programs have their own benefits as well. So when I saw this blog post on PerryGeo complaining about an article about free GIS programs in the latest issue of American Surveyor magazine, I guessed it wasn’t as bad as he thought it was. Well, I read it, and it isn’t as bad – it’s much, much worse. I’d go so far as to call it a classic example of the Dunning-Kruger effect in action.

The article purports to be a representative survey of “simple to use” GIS, “easy to find on the Internet, readily available, easy to download and easy to install”. The software needed to be able to load in georeferenced vector and raster imagery in standard GIS formats, let you edit/create layers, do some basic analysis, and let you export the map in some reasonable format. From the many dozens of free GIS software packages available online that  meet these requirements, he could only come up with four:

The selection of Google Earth for this article is a joke. I love Google Earth, but it’s not even close to a true GIS, and right from the start it should have been evident that it couldn’t perform most of the functions he wanted; evaluating it here is a waste of time and space. ArcGIS Explorer is marginally better, but for the intended uses, it doesn’t cut it. That leaves DIVA-GIS and Quantum GIS as the only two legitimate contenders. I’ve played with DIVA-GIS a bit, and it’s a good free GIS program, even beyond its primary function for analyzing geographic and environmental factors for species distribution. But to consider this program as a prominent example of what’s available in the free GIS world is nonsense.

But it’s what he does to Quantum GIS that’s the real crime. He dismisses it as “too complicated to use right out of the box”, and says that based on the documentation the program won’t do what he wants it to. The author claims to be head of GIS and mapping for a consulting company, and yet he can’t even find the “Add Vector Layer” and “Add Raster Layer” buttons prominent in QGIS’s toolbar? Can’t change the layer properties, which isn’t that much different from DIVA-GIS’s approach? Can’t check out the toolbar buttons that provide virtually all the functionality that he says he’s looking for? In the table that compares functionality between different programs, he puts question marks in most of Quantum GIS’s column, even though it wouldn’t take a  “GIS expert” very long to figure out that Quantum GIS could perform most of those. DIVA-GIS is a nice piece of software, but Quantum GIS is clearly superior. Condemning Quantum GIS without a fair evaluation doesn’t serve the article’s readers very well.

The author tries to hide behind some weasel clauses. He claims that this isn’t meant to be a comprehensive review, as his rationale for covering only a few programs. I call BS on this; if you don’t have the basic background necessary to write such an article and can’t be bothered to do the research needed,  then pass it on to someone who has the expertise or time to do a good job. He also claims that if someone unfamiliar with these topics can’t use the program “right out of the box”, without spending some time learning how to do things, that’s an indication that the software is too complex. Total BS; that’s like telling someone who’s used to Microsoft’s primitive word processor WordPad that Microsoft Word isn’t worth learning, because you’ll need to spend some time learning some of the more advanced functions.

What’s more, the data he  uses for his example requires some level of user sophistication. They have to know the difference between raster, vector and DEM data, and understand the concepts of georeferencing for all those data types. The concepts behind the functionality he wants aren’t trivial, either; he wants software that can do buffering and network analysis, as well as information searches. This isn’t rocket science, but it isn’t intuitively obvious, either; anyone who understands these concepts has to be reasonably well-informed about GIS issues. The author’s implication is that his readers aren’t smart enough to be able to figure out a program unless it’s trivially easy to use, which is really an insult to them. But if they understand the data concepts, they’re smart enough to be able to spend a little time figuring out the program.

I’m not surprised PerryGeo is pissed off; years of work has gone into making Quantum GIS a first-rate free GIS program, but the author of this article blows it off completely without a fair evaluation. And he does his readers a disservice not just by denigrating Quantum GIS, but also by implying that he’s done a representative evaluation of free GIS options, something the article doesn’t even come close to doing. What an embarrassment.

End of rant.