Mapping Africa

We're always looking for geospatial data to teach with. Finding data for the U.S. is relatively easy, but finding data for other places has often been more challenging. AfricaMap is a web mapping interface created by Harvard University's Center for Geographic Analysis that can be used stand-alone in a classroom because there is a rich set of data available for viewing. The layers that I looked at, some shown below, drew quickly and came with a legend(!). Very nice accomplishment for CGA after being in operation just under three years. Here is a description of the AfricaMap project:

"AfricaMap is based on the Harvard University Geospatial Infrastructure (HUG) platform, and was developed by the Center for Geographic Analysis to make spatial data on Africa easier for researchers to discover and explore.

This project attempts to address a basic problem for all scholarship on Africa that treats where things happen as necessary to understanding how and why they happen: finding places on a map. Despite the existence of excellent public maps for Africa, to date there is no common source that allows students, researchers, and the general public to:

1. Interact with the best available public data for Africa
2. See the whole of Africa yet also zoom in to particular places
3. Accumulate both contemporary and historical data supplied by researchers and make it permanently accessible online
4. Work collaboratively across disciplines and organizations with spatial information about Africa in an online environment"

Sounds great! Here are some maps available through the AfricaMap site and some comments on how to use the site.

The above map is the 1722 Delisle Carte d'Afrique found under Map Layers -> Historic Maps 1600 to 1800. I lead with this map because I love old maps.

This map shows a map of ethnolinguistic families (mapped in 2001). Remember to add the Legend found over to the right in Map Layers.

Under the Environmental layer, you will find just three layers, rivers, soils and, shown above, surficial geology. Note that this legend is not all that useful.

AfricaMap allows for downloading of their data, but only some of the layers are currently available. That may be, in part, why they this web map is in beta. How to get to the download function: Click on Map Layers, scroll all the way over to the right. There is a Download tab, don't click there, follow the arrow down to your layer and click "download" there. If the data are available, you will be taken to the web page and source of the geospatial data, if not available, you will be given this message "Mapping data will be made available for download." That is quite hopeful.

Thanks go to Diana Sinton for sharing this web map site.

Adding a Map to Your Web Page - From ESRI

There are many ways to add a map to a web page. Here is one more from ESRI. It's called Mapping For Everyone and it is in Beta. This is U.S. only.

What you see above is a choropleth map of the City of Poughkeepsie (New York) by unemployment rate, a rather hot topic! This is tract-level data. The data source is "estimated July 1, 2009 unemployment rate in the United States." There are currently only seven different demographic variables to map, but since this is in beta and since people love to map demographics of all sorts, my guess is that ESRI will add more data.

Here's what you do:

1) Enter a zip code, then 2) choose a demographic variable from the drop-down list, 3) size your map to the dimensions of your web page (for instance, the map above is 500 pixels wide), then 4) share your map, either as a link, or as html code to embed into your web page.

Thanks for the tweet, Joseph Kerski!

Part II: Calculating Point Locations

I probably posted my blog post, Calculating Point Locations from One Known Point, Distance and Direction, too soon. I got some more great advice from Andy Anderson at Amherst College, who said it was okay if I shared this here. He calculated out the trig for me. Thanks, Andy!

Here's my solution, which stays in ArcGIS, and may well be more accurate in general than the other two solutions you found (i.e. do you know exactly what procedure Map Maker is using?). In general this isn't a simple problem. It can be approximated either by projecting the coordinates such that there is low distortion over the region covered by the lines, or by assuming a spherical Earth and using spherical trigonometry. The other issue is that a rhumb line is not in general the same as a geodesic, though again over a small region they are basically the same.

I'm going to assume that you are working over a small region. Here's one way to do it, using the Mercator projection, which by design keeps rhumb lines correct, or another way to say it is that a 1-m change in x will cover the same distance on the map as a 1-m change in y.

1) Format your data more or less as follows in a file that ends with .csv:

Longitude,Latitude,Length_m,Dir_deg
-72,43,100,30
-72,43,96,15
...

The length is assumed to be meters, direction in degrees clockwise from north (i.e. the azimuth). The central point is repeated here since it might conceivably change and because the calculations we'll use to generate the distant points all start with that point.

2) Open ArcGIS, preferably a new blank document, then double-click on the data frame (usually named Layers), click on the tab Coordinate System, and navigate to Predefined > Projected Coordinate Systems > World > Mercator (world). This version is based on the datum WGS 84.

3) Menu Tools > Add XY Data... , and import the CSV file; in the dialog assign the correct datum for the above geographic coordinates. If it's not the same as WGS 84, pick an appropriate transformation. The data will be added as (file name) Events.

4) Right-click on (file name) Events and menu Data > Export Data… In the resulting dialog, in the button group Use the same coordinate system as:, click on the data frame. Choose a name and location for the shapefile and click the button OK. When you are asked Do you want to add the exported data to the map as a layer?, click on the button Yes.

5) Open ArcToolbox, then navigate to Data Management Tools > Features and double-click on Add XY Coordinates. In the menu Input Features, select the new shapefile and then click on the button OK. When the tool completes, click on the button Close.

6) Right-click on the new shapefile and menu Open Attribute Table. Two new fields will be present, POINT_X and POINT_Y, which will be Mercator coordinates in meters. Click on the button Options and menu Add Field..., and create a field with the Name: (for example) DISTANT_X with Type: Double. Repeat to create a field with the Name: DISTANT_Y.

7) Right-click on the header of the field DISTANT_X and menu Field Calculator…. In the field DISTANT_X =, type and/or click:

[POINT_X] + [Length_m] * Sin( [ Direction] * Atn(1) / 45 )

Then click the button OK. Now right-click on the header of the field DISTANT_Y and menu Field Calculator….
In the field DISTANT_Y =, type and/or click:

[POINT_Y] + [Length_m] * Cos( [ Direction] * Atn(1) / 45 )

Then click the button OK. Note that the trig functions Sin and Cos are reversed from the "usual" because the angle is azimuthal.
The trig functions "Atn(1)/45" is equal to the degree-radian conversion factor π/180.

8) DISTANT_X and DISTANT_Y are the new point positions. You can now turn them into their own point layer in ArcToolbox by navigating to Data Management Tools > Layers and Table Views and double-clicking on Make XY Event Layer. Choose your shapefile as the XY Table and DISTANT_X and DISTANT_Y as the X Field and Y Field. Choose a name for the layer, and choose the Spatial Reference as Mercator (world) (probably easiest to import it from your shapefile). Click OK.

9) Due to a bug in ArcGIS, the Distant Point layer will not appear in the Table of Contents, which means you can't select it and export it immediately as a shapefile (as in Step 4 above). However, you can save it as an external layer file with ArcToolbox by navigating to Data Management Tools > Layers and Table Views and double-clicking on Save to Layer File; it will appear in the menu Input Layer. Then add it to ArcGIS. This file refers to the shapefile you created for its data, so don't let them get separated. Or, you can now export this file as in Step 4 above.

Andy then suggests that this could be streamlined in Model Builder, as I suggested in my question to the the New York GIS Help Desk. It's so reassuring having smart friends and colleagues!

Also, one more thing. This project is one in which a graduate student is marking conch locations and movements underwater. She is making the measurements alone, diving with scuba gear, and the distances are rather short, less than 15 meters. Cool, huh?

Calculating Point Locations from One Known Point, Distance and Direction

I put a call for help out on Twitter and on my posterous blog with a geospatial problem a UWI-CERMES student needed some help with. Though I called it a GIS question, I was called out for not saying explicitly that it was an ArcGIS question. After doing some web-digging and fumbling with the software and what I thought might work, I submitted my question to the always helpful New York State GIS Help Desk. I got an answer within a few hours (thanks, you're the best!). This service is available for those lucky enough to be in the great state of New York.

Here is the question and answer responses.

Question:

I have a known location point (latitude and longitude) which is my base station [shown as X, above]. I have points scattered around this known location [red points, above]. If I know the orientation direction (or angle or deflection) to each point from the base station and I know the length (distance) [blue lines, above], can I use ArcGIS to get the latitude and longitude of each point? I would like to automate this, if possible, in model builder as I have hundreds of these points to calculate. I tried the Distance-Direction tool but it doesn't seem to save my new endpoint to a table that I created. Plus I'd like to many of these, ideally, not one-by-one.

Answer:

Using out of the box functionality, you can create two-point lines by first clicking on the base point and then using the direction/length command to enter the parameters of the end point. You can then convert the nodes to points. Unfortunately, this interactive approach might not be ideal if you have many points to create. An alternative to this is to use a tool available in the ET GeoWizards extension (a third party extension available from ET Spatial Techniques) called Lines from Points, Directions and Distance that automates this process. Before running the tool you will need to create copies of the base point (one for each radial, or point scattered around the base) during an edit session, and then add the values for direction and distance to new fields for each entry in the attribute table (you could do this by manual entry or copy/paste after opening the attribute table in Microsoft Excel). The tool will then create lines radiating from the base point to the entered distance/directions. The lines can then be converted to points using the Polyline to Point tool in this same extension. For more information on the ET GeoWizards extension, http://www.ian-ko.com

I got some similar feedback from the Twitter community. Thanks, Laura Cerquozzi (geographygeek) for this:


That seemed like reasonable advice. I'd give the ET Geowizards extension a try, see if there was a free trial version to use.

Ready for work with all my new advice from the geospatial community, I came into the office Friday afternoon and popped my head into the office of the folks having the geospatial issues. They had already figured it out using Map Maker Pro. I have never used Map Maker Pro not had I even heard of it prior to coming to the UWI. Map Maker Pro is a GIS software for Windows OS created out of the U.K. They must have hopped on that domain name early! There is also Map Maker Gratis. Looks like I'm learning a lot already!

To make this Map Maker Pro solution work for this problem, one needs to create a comma-delimited table that has the Direction and Distance for each point. Ideally, one also has a description-of-point column. In Map Maker, one has the known point, or base station, that one points to and then runs a calculation on the created table. The output file (in DBF format) gives the latitude and longitude of each point.

This problem goes down in the annals of Why Does It Have to be so Hard? using tools we already have. I scratch my head in wonder.

ADDED Oct 6, 2009: New information on how to calculate this problem using ArcGIS.

Geospatial Conference a Success

Last week was the NITLE Geospatial Technologies in the Liberal Arts conference at Skidmore College. I mentioned the conference agenda here. Please read about the details of how the conference came out here at the NITLE blog and written by Sean Connin. Talks on open source GIS options, web mapping, virtual globes in teaching, mobile technologies, geospatial literacy, birds of a feather, mingling with other geospatial technologists, plus a keynote by Adena Schutzberg, Executive Editor of Directions Magazine. I wish I could have been there. Well done, folks!

Added Oct 5, from All Points Blog, Directions Magazine conference by Adena, with the great line at the end: "many even understand how (GPS) works. But, no one really knows what : A recap of the NITLE GeospatialGIS is." Too true.

Tablet PC News...NOT from Apple

There was a minor amount of techno buzz a couple of weeks ago here and here when Apple raised the notion that they, in fact, were going to be coming out with their long-last tablet PC offering. I didn't really believe it because it is something I've heard since getting our marvelous Windows-based Compaq/HP TC1100 tablets back in 2004. Many higher educators kept holding their collective breath waiting for the Mac version.

I did blog about the first semi-real version of the Mac tablet. I didn't bother with the recent rumors.

But this new tablet PC buzz out of Gizmodo and video shows what looks like a larger iPhone, a slicker-looking Kindle/e-book reader and a touch/pen-based device. Maybe it's like an affordable and mini version of the Surface? But it's called Courier and comes from Microsoft.

Looks like the Courier, if the rumors are correct, could be a pretty nice mobile device. Doing GIS with a finger touch, anyone!?

Thanks, Tablet PC blog and OgleEarth (I didn't know Stephan Geens was a tablet enthusiast!) for pointing this out.

Coral Reef mapping with ReefBase

I was directed to the ReefBase website while contributing to a colleagues research and found it useful not only for the ReefGIS Online mapping application but also for the ability to download GIS data sets. The online mapping application made it easy for me to determine if the available data suited my needs.

Dutchess County's website nationally recognized

The Center for Digital Government and the National Association of Counties (NACo) recognized the Dutchess County government as the second-most digitally advanced county government in the country. Interactive website mapping applications, ParcelAccess and GeoAccess helped contribute to the popularity of the Dutchess County website. ParcelAccess enables users to easily obtain tax parcel and assessment data. GeoAccess provides selectable layers on various infrastructure throughout the county including schools, recreation sites and historic sites.
Thanks to the Dutchess County Planning and GIS Department for providing such a great resource!

A Little Press for a Geospatial Instructional Technologist

My local newspaper, the Poughkeepsie Journal, published an announcement about my upcoming Fulbright to the University of the West Indies in yesterday's paper and All Points Blog got a hold of it. Thanks for posting this, Adena! I hope to meet you some day soon.

No, you do not have to be a faculty member to earn a Fulbright grant.

But I found this blog post from a tweet from FulbrightSchlrs, who wisely thought to send this info along to @vassarnews. Hint!

NITLE GIS Conference Agenda Announced

As mentioned in a previous post, NITLE will hold a Geospatial Technologies conference September 25 to 27, 2009 at Skidmore College. This conference is designed for NITLE school members who wish to learn more about geospatial technologies and network with those who support and do GIS and other geospatial tools.

The conference planners, all terrific and hard-working geospatial professionals at liberal arts colleges, designed an excellent program. To review the agenda, please visit the Geospatial Technologies conference website or go directly to the agenda document. This is a working document and may be subject to minor change.

The deadline for registration is August 28th, 2009 - one week from this Friday. For your convenience, 20 rooms have been reserved at the The Saratoga Hilton at a special NITLE rate of $179 (plus sales and occupancy taxes), please call 518-693-1005 by August 25, 2009. After August 25th the rate and room availability cannot be guaranteed.

For more information, contact one of the conference planners:

Andy Anderson, Amherst College

Jon Caris, Smith College

Alex Chaucer, Skidmore College

Jenni Lund, Wheaton College

Sharron Macklin, Williams College

David Tatem, Trinity College

Bird Research at Vassar Using GIS

The URSI (Undergraduate Research Summer Institute) summer program at Vassar teams Vassar professors with a student or students interested in a compelling research project. Check out Prof. Mary Ann Cunningham and Earth Science major Laurel Walker VC '11 working on a bird project and using GIS to bring it all together. Mary Ann teaches the GIS classes at Vassar. Plus you can also check out Vassar's GIS Lab!