Posts Tagged ‘Mapping’

Plan Your Trip through the Roman Empire with ORBIS

Wednesday, June 27th, 2012

If you wanted to know the fastest route from Roma to Londinium in June of 300 AD or how much it would cost to ride the shortest distance at ox cart speed to Constantinopolis, check out ORBIS. Researchers at Stanford have created a model of Ancient Roman transport networks over land and sea composed of 751 points (cities, landmarks, mountain passes) and thousands of linkages.

The model simulates the average distance of a large group of travelers taking a given route in a given month. The frictions of distance, terrain, climate, and monetary expense are all accounted for in the model and you have the ability to set many of the options. The technical aspects of the project as well as its historical bases are thoroughly documented. The output consists of route maps (which you can download as KML or as CSV) and interactive cartograms. The platform is an open source stack – PostgreSQL with PostGIS, Open Layers, Geoserver, and some JavaScript libraries.

Check it out at http://orbis.stanford.edu.

The fastest route from Roma to Londinium in June? A boat ride across the Mediterranean to Narbo, foot/army/pack animal across southern Gaul, and a coast-hugging boat ride from Burdigala will get you there in 26.6 days and 2,974 kilometers. That carriage to Constantinopolis would cost you about 2,087 denarii and would take 128 days at ox cart speed – perhaps you should consider a fast military march instead?

2010 Census Generalized Cartographic Boundary Files

Thursday, December 22nd, 2011

I’ve had a few interesting projects that have kept me busy at the end of this year. I’ll do a post or two after New Years, once I’m back in the office and can take some screen shots to illustrate.

In the meantime I have one tidbit I can mention – the Census Bureau has released the 2010 version of the Generalized Cartographic Boundary Files. These files are generalized versions of the TIGER files, with smoothed and simplified boundaries and areas of coastal water removed. They haven’t posted them on the same page as the 2000 and 1990 boundaries; they’ve mentioned they’re creating a new interface to host all of them, which is currently a work in process at http://www.census.gov/geo/www/cob/.

However, you can get access to all the 2010 boundaries via the FTP site – you just need to know what you’re looking at. All the files are named with codes to identify the geographic coverage, summary level, and resolution / scale. There’s a README file on the FTP page that tells you how to identify each.

But in brief – The file names look like this: gz_2010_ss_lll_vv_rr.zip, where:

  • ss is the state INCITS / FIPS code which you can look up here – ‘us’ is a national level file.
  • lll is the summary level or unit of geography – the README file has a table with each code. The most common ones: 040 for state, 050 for county, 060 for county subdivisions, 140 for census tracts, 160 for places, 310 for metropolitan and micropolitan statistical areas, 860 for ZCTAs. (No PUMAs- 2010 PUMA boundaries haven’t been drawn yet, and 2000 PUMA boundaries are still being used in the latest ACS).
  • vv is a version number for the file.
  • rr is resolution – most of the files are 500k = 1:500,000, which is the least generalized and best for mapping state-level to regional areas. For national level files you also have the option of 5m = 1:5,000,000 and 20m = 1:20,000,000, which are more generalized and better for national mapping.

The Census Bureau has been doing a lot of tweaking to their website lately. The legacy version of the American Factfinder is set to disappear for good on Jan 20, 2012.

Mapping Hard to Count Areas for Census 2010

Tuesday, February 23rd, 2010

There was an interesting article in the New York Times today about neighborhoods in New York that typically get under-counted in the Census. These include areas with high immigrant populations as well as places that have had new construction since the last census, as the buildings haven’t been added to the Census Bureau’s master address file.

What the article didn’t mention is that CUNY’s Center for Urban Research has created a great online ap called the Census 2010 Hard to Count mapping site. The site is built on the Census Bureau’s Tract Level Planning Database, which identified twelve population and housing variables, such as language isolation, recent movers, poverty, and crowded housing, that were associated with low mail response in the 2000 Census. This tool was designed to help Census reps, local government officials, and community activists identify traditionally under-counted areas to insure a more complete count this time around.

The database is national in scope, and you can easily map tracts for a particular state, county, city, metro area, or tribal area, and you can search for an area using an individual address. The map is built on a Google Maps interface, and zooming in will change the units mapped from larger units (states, counties, etc) to tracts. You can easily select one of the twelve variables color-coded in the menu to the left of the map, or a Hard to Count index of all the variables.

Reading List for Geographic Information Course

Saturday, August 29th, 2009

The fall semester is here, and I’m about to start teaching the class I mentioned in my last post (an information studies course on geographic information). I thought I’d share my reading list and try out the Open Book plugin. I chose my readings based on: my particular audience (undergraduate students from many disciplines with little or no background in geography), relevance (materials appropriate in a hybrid information studies / geography course), cost (wanting to assign the students a single textbook that’s reasonably priced and covers all the bases, and will supplement with other readings), and copyright (staying within the bounds of fair use by not assigning too much from a single work). Here goes:

[openbook]1593852002[/openbook] I decided to go with Krygier and Woods Making Maps as my assigned text book. Since cartography is a visual and technical art, I thought it made sense to use a book that relies on visuals for explanations rather than text. It’s approachable, particularly for my students who won’t be coming from a geography background, affordable, wonderfully quirky, and covers all of the essentials of the geographic framework and map interpretation and design independent of specific GIS software.

[openbook]1405106727[/openbook] I’m using the first chapter of Cresswell’s book as a succinct introduction to how individuals define places, but would recommend the rest of the text for classes that cover geographic concepts and methods.

[openbook]026208354X[/openbook] I’m assigning the second and third chapters of Hill’s book. The second chapter, which discusses how people process, store, and use geographic information is the best summary of this topic that I’ve ever seen, and the third chapter is a good overview of the different types of geographic objects. As a librarian-geo nerd, I love the chapters that deal with coordinate metadata and gazetteers, but won’t be using them in this class.

[openbook]0262620014[/openbook]This is an urban planning / design classic, and I’ll have my students read the summary of Lynch’s city elements (based on his research, Lynch proposed that people mentally break the urban environment down into five types of elements in order to organize and navigate the city: paths, barriers, districts, nodes, and landmarks).

[openbook]0470129050[/openbook]This is the only traditional textbook that I’ll be borrowing from (I actually used it when I was a Freshmen, way back when). While I’m using the previous three books to discuss egocentric places, or how we as individuals conceive of place, I’m using the first chapter of this book to give the students an overview of geocentric places – the formal, defined hierarchy of places that exist in the world – and to introduce them to the concept of regions.

[openbook]0226534146[/openbook]This has become a modern classic and I almost assigned it as a second textbook. I am assigning the chapter on maps for propaganda as a background to our discussion on map interpretation and communication, and will later use the chapter on census maps to talk about the effects of data classification and choice of enumeration units.

[openbook]1934356069[/openbook]This is the only software book that I’ll be using chapters from, so the students have some formal guide for using QGIS (in addition to the QGIS documentation). I’m using the chapters on vector and raster data.

[openbook]1412910161[/openbook]This concise, excellent book deals strictly with the concepts and principles behind GIS. I’m using the chapters on spatial search and geoprocessing, but would recommend the entire book for any GIS course, novice to advanced.

In addition to chapters from these books, I’ll also be using:

  • “Revolutions in Mapping” by John Noble Wilford, National Geographic Feb 1998 – a great overview of the history of cartography
  • USGS GIS poster – if there is such a thing, this is a “web classic” and an accessible intro to GIS
  • One article from a scholarly journal and one article from a mass market magazine to illustrate how geographic research is covered and used
  • And for shameless self-promotion, I summary I wrote about US Census data – In Three Parts

Finally, an honorable mention:

[openbook] 1593855664[/openbook] If I was teaching an introductory GIS course in a geography or earth sciences department, this is certainly the book I would use, and for those of you in that boat I’d recommend checking it out. It does an excellent job of covering GIS principles without being software specific, contains exercises at the end of each chapter, and is well written and affordable. Since the scope of my course is broader than GIS and my audience more general and diverse, I opted to leave it out (but may still assign a chapter).

Print Composer in QGIS – ACS Puma Maps

Sunday, July 12th, 2009

ny_youth_pumasI wrapped up a project recently where I created some thematic maps of 2005-2007 ACS PUMA level census data for New York State. I decided to do all the mapping in open source QGIS, and was quite happy with the result, which leads me to retract a statement from a post I made last year, where I suggested that QGIS may not be the best for map layout. The end product looked just as good as maps I’ve created in ArcGIS. There were a few tricks and quirks in using the QGIS Print Composer and I wanted to share those here. I’m using QGIS Kore 1.02, and since I was at work I was using Windows XP with SP3 (I run Ubuntu at home but haven’t experimented with all of these steps yet using Linux). Please note that the data in this map isn’t very strong – the subgroup I was mapping was so small that there were large margins of errors for many of the PUMAs, and in many cases the data was suppressed. But the map itself is a good example of what an ACS PUMA map can look like, and is a good example of what QGIS can do.

  • Inset Map – The map was of New York State, but I needed to add an inset map of New York City so the details there were not obscured. This was just a simple matter of using the Add New Map button for the first map, and doing it a second time for the inset. In the item tab for the map, I changed the preview from rectangle to cache and I had maps of NY state in each map. Changing the focus and zoom of the inset map was easy, once I realized that I could use the scroll on my mouse to zoom in and out and the Move Item Content button (hand over the globe) to re-position the extent (you can also manually type in the scale in the map item tab). Unlike other GIS software I’ve experimented with, the extent of the map layout window is not dynamically tied to the data view – which is a good thing! It means I can have these two maps with different extents based on data in one data window. Then it was just a matter of using the buttons to raise or lower one element over another.
  • Legend – Adding the legend was a snap, and editing each aspect of the legend, the data class labels, and the categories was a piece of cake. You can give your data global labels in the symbology tab for the layer, or you can simply alter them in the legend. One quirk for the legend and the inset map – if you give assign a frame outline that’s less than 1.0, and you save and exit your map, QGIS doesn’t remember this setting if when you open your map again – it sets the outline to zero.
  • Text Boxes / Labels – Adding them was straightforward, but you have to make sure that the label box is large enough to grab and move. One annoyance here is, if you accidentally select the wrong item and move your map frame instead of the label, there is no undo button or hotkey. If you have to insert a lot of labels or free text, it can be tiresome because you can’t simply copy and paste the label – you have to create a new one each time, which means you have to adjust your font size and type, change the opacity, turn the outline to zero, etc each time. Also, if the label looks “off” compared to any automatic labeling you’ve done in the data window, don’t sweat it. After you print or export the map it will look fine.
  • North Arrow – QGIS does have a plugin for north arrows, but the arrow appears in the data view and not in the print layout. To get a north arrow, I inserted a text label, went into the font menu, and chose a font called ESRI symbols, which contains tons of north arrows. I just had to make the font really large, and experiment with hitting keys to get the arrow I wanted.
  • Scale Bar – This was the biggest weakness of the print composer. The scale bar automatically takes the unit of measurement from your map, and there doesn’t seem to be an option to convert your measurement units. Which means you’re showing units in feet, meters, or decimal degrees instead of miles or kilometers, which doesn’t make a lot of sense. Since I was making a thematic map, I left the scale bar off. If anyone has some suggestions for getting around this or if I’m totally missing something, please chime in.
  • Exporting to Image – I exported my map to an image file, which was pretty simple. One quirk here – regardless of what you set as your paper size, QGIS will ignore this and export your map out as the optimal size based on the print quality (dpi) that you’ve set (this isn’t unique to QGIS – ArcGIS behaves the same way when you export a map). If you create an image that you need to insert into a report or web page, you’ll have to mess around with the dpi to get the correct size. The map I’ve linked to in this post uses the default 300 dpi in a PNG format.
  • Printing to PDF – QGIS doesn’t have a built in export function for PDF, so you have to use a PDF print driver via your print screen (if you don’t have the Adobe PDF printer or a reasonable facsimile pre-installed, there are a number  of free ones available on sourceforge – PDFcreator is a good one). I tried Adobe and PDFcreator and ran into trouble both times. For some reason when I printed to PDF it was unable to print the polygon layer I had in either the inset map or the primary map (I had a polygon layer of pumas and a point layer of puma centroids showing MOEs). It appeared that it started to draw the polygon layer but then stopped near the top of the map. I fiddled with the internal settings of both pdf drivers endlessly to no avail, and after endless tinkering found the answer. Right before I go to print to pdf, if I selected the inset map, chose the move item content button (hand with globe), used the arrow key to move the extent up one, and then back one to get it to it’s original position, then printed the map, it worked! I have no idea why, but it did the trick. After printing the map once, to print it again you have to re-do this trick. I also noticed that after hitting print, if the map blinked and I could see all the elements, I knew it would work. But, if the map blinked and I momentarily didn’t see the polygon layer, I knew it wouldn’t export correctly.

Despite a few quirks (what software doesn’t have them), I was really happy with the end result and find myself using QGIS more and more for making basic to intermediate maps at work. Not only was the print composer good, but I was also able to complete all of the pre-processing steps using QGIS or another open source tool. I’ll wrap up by giving you the details of the entire process, and links to previous posts where I discuss those particular issues.

I used 2005-2007 American Community Survey (ACS) date from the US Census Bureau, and mapped the data at the PUMA level. I had to aggregate and calculate percentages for the data I downloaded, which required using a number of spreadsheet formulas to calculate new margins of error; (MOEs). I downloaded a PUMA shapefile layer from the US Census Generalized Cartographic Boundary files page, since generalized features were appropriate at the scale I was using. The shapefile had an undefined coordinate system, so I used the Ftools add-on in QGIS I converted the shapefile from single-part to multi-part features. Then I used Ftools to join my shapefile to the ACS data table I had downloaded and cleaned-up (I had to save the data table as a DBF in order to do the join). Once they were joined, I classified the data using natural breaks (I sorted and eyeballed the data and manually created breaks based on where I thought there were gaps). I used the Color Brewer tool to choose a good color scheme, and entered the RGB values in the color / symbology screen. Once I had those colors, I saved them as custom colors so I could use them again and again. Then I used Ftools to create a polygon centroid layer out of my puma/data layer. I used this new point layer to map my margin of error values. Finally, I went into the print composer and set everything up. I exported my maps out as PNGs, since this is a good image format for preserving the quality of the maps, and as PDFs.

GIS and Mapping Titles

Friday, April 25th, 2008

I’ve been building the library’s collection of geography, GIS, and demography books, and many of them have started arriving. I thought I’d share some of best picks with everyone. Here’s a subset of some of the GIS titles (and more are on the way!)

A to Z GIS : an illustrated dictionary of geographic information systems 2nd ed
Wade, Tasha and Sommer, Shelly
ESRI Press, 2006
Convenient print copy of ESRI’s online glossary, with nice illustrations.

Beyond mapping : meeting national needs through enhanced geographic information science
National Research Council (U.S.). Committee on Beyond Mapping
National Academies Press, 2006
A concise overview of GIS: where it’s been, where it is, where it needs to go, and why.

Elevation data for floodplain mapping
National Research Council (U.S.). Committee on Floodplain Mapping Technologies
National Academies Press, 2007.
The specific topic is quite salient, but this book also serves as great intro to rasters and remote sensing in general.

Geographic information systems demystified
Galati, Stephen R
Artech House, 2006.
A non-ESRI overview of GIS. It’s been checked out since it arrived, so it must be good!

Georeferencing : the geographic associations of information
Hill, Linda L.
MIT Press, 2006.
This is what I’m reading now. It covers spatial cognition, digitization, coordinates, ontologies, gazetteers, metadata, info retrieval, and more.

Getting to know ArcGIS desktop : basics of ArcView, ArcEditor, and ArcInfo 2nd ed., updated for ArcGIS 9.
Ormsby, Tim, et. al.
ESRI Press, 2004
At this point, the old stand-by introduction to ArcGIS

Making maps : a visual guide to map design for GIS
Krygier, John and Wood, Denis
Guilford Press, 2005
Easy to read and cleverly organized overview of cartographic conventions and design for GIS

Statistical methods for geography : a student guide 2nd ed.
Rogerson, Peter A.
Sage Publications, 2006.
Nice overview of this topic with many examples.

Hands-on GIS Census Workshop

Thursday, April 10th, 2008

I’ve posted the tutorials from the workshop I gave the other day for the NYCRDC. I’ve created a Resources page to hold resources hosted on this site – you can find them there, along with the datasets.

Overall I think it went rather well, but it was way too much material for a three hour workshop! We covered the intro slides, and Part I (Intro to GIS and ArcMap). I did an abridged version of Parts II (Intro to Layout View) and III (finding and downloading data, ArcCatalog, preprocessing in Excel) rather than doing all of II and none of III. The third part covers a lot that the standard ArcGIS texts gloss over (or leave out all together), so I really wanted to cover some of that material. But I couldn’t omit any of the basics in the first two parts, because you really need to know them before you can delve further (and understand why you’re delving). Ahhh, the steep learning curve of GIS!


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