NW WA GIS User Group Presentation

The NWWAGIS User Group meeting in Bellingham on Friday was really great. There were lots of interesting people to meet and talk with (including a client I had not yet met in person!), some excellent presentations, and lots of good discussion.

An impromptu presentation by Greg Sutherland of San Juan County was particularly noteworthy--he showed a YouTube clip of a demo the PPI Group did for San Juan County Public Works. They showed up on the 10:00 am boat, drove their special data collection vehicle around Friday Harbor for a couple of hours, and prepared a demo by 1:00. They collected multi-angle high-resolution photos (similar to the Google StreetView photos) and a very dense LiDAR point cloud. The end result? Engineers are able to take measurements of rights-of-way, cross walks, stop signs, utility poles, you name it, all from a street-level photo. I think the video might be 'invite only' since PPI is courting San Juan county as a client, but once I find the link I'll post here.





My talk seemed to go fairly well, and I received some positive feedback afterwards and lots of helpful suggestions about some of the trickier analytical questions. Here is a PDF if you would like to check it out. Many thanks to Dan Siemann and all of the folks at the National Wildlife Federation for asking me to work on this interesting project, and the Mountaineers Foundation for providing some of the funding.

CORE GIS--Live!

I will be giving a presentation tomorrow in Bellingham to the Northwest Washington GIS User's Group.

March 18th, 2011
9:00-12:00 am
City of Bellingham, Fireplace Room
625 Halleck St, Bellingham

Click here for a PDF map.

I'll be talking about some recently completed work I did for the National Wildlife Federation examining floodplains, flooding, and wildlife. I'll post the presentation here and on the website next week.

Great Data, Byzantine Retrieval System

I am working on a series of maps for the Sierra Club's Resilient Habitat's campaign. The maps have been great fun and cover geography that I haven't mapped in awhile. The most recent map covers the Greater Everglades ecosystem, and since the habitat extent includes a substantial portion of the Atlantic ocean and Gulf of Mexico, we thought it might add visual interest to show bathymetry.

After doing a bit of research, I found a great source for integrated terrain and bathymetry at the NOAA coastal relief site. I found my area of interest, clicked on the link to download the data, and was somewhat surprised to see no obvious way to download the data--no 'download' button, no FTP link, nothing. I did notice a 'Create Custom Grid', but since I wanted all of the data shown in the map, that seemed like a hassle. So I called NOAA, and to my utter astonishment, reached an extremely helpful human being on my first attempt. She didn't know how to obtain the data either, but transferred me to someone who did.



Turns out, the ONLY way to obtain the data is by the 'Create Custom Grid' button, even if you want the whole enchilada. But it gets better--you can't specify the whole extent in the create custom grid dialogue, because the extractor limits your request to about 8,000 cells in either direction. So, I had to split the grid into fourths. Here are my notes outlining how to do that:



The grids are extracted and exported as ASCII text files, which I imported to ArcGIS GRIDs. But there's another catch: the upper value of each grid showed up as 65,535. This did not seem like a plausible elevation value (unless the Z values were in centimeters?!) so after a bit of Googling found this helpful post by Thomas Ballatore on the ESRI Support website. This is in response to someone working with SRTM data, but the same procedure worked equally well on the NOAA coastal relief data:

The SRTM files contain values from 0 to 65535. In a given SRTM tile, most of the values will be "typical" elevation values like the 1,133m and below you mention. However, areas where there is no data (voids) are assigned a value of 32768. The setnull command mentioned above would indeed set those values to "nodata".

HOWEVER, the SRTM data also correctly contains areas below sea level. These are reported as decreasing values from 65536. For example, an elevation of -2m would have a value of 65534, and elevation of -10 would be 65526 and so on.

For every country I have worked with that has a coastline, there will be a number of these along the coastline. Whether they are truly below sea level or if that is just an inaccuracy of the SRTM data would require further investigation.

Anyway, if you set all values greater than 1133 to nodata, then you will incorrectly set these negative values also to nodata. To avoid that, I use the following two steps in Raster Calculator to correctly prepare the SRTM data:

Step 1. Execute the following:

setnull([N30E119.bil] == 32768,[N30E119.bil])

where N30E119.bil is an SRTM file I was recently working with...change this to your tile's name. This will set the voids to nodata.

Step 2. Then execute this:

con([N30E119.bil] > 32768,[N30E119.bil] - 65536,[N30E119.bil])

This will correctly convert the negative values to negative values. Remember that spaces are important in raster calculator!

After running this on each of my four grids, I mosaiced them into a single grid, derived some hillshade, and was good to go.



Once the Florida Resilient Habitats map is finalized and Sierra Club has signed off on it, I will post it here.

The Ephemeral Nature of Maps in our Modern Age

I've been thinking a lot about history these past several weeks, primarily because of the historic mapping work I described in an earlier post, but also because I am reading The Pirate Hunter by Richard Zacks. This excellent book is the true-life account of Captain Kidd, and it is based on painstaking research Zacks undertook for nearly three years, poring over historical documents, letters, diaries, newspapers, etc. Yes, it was time consuming and occasionally difficult work, but it was possible for Zacks to do the research because once he located a document, he could actually read it--or have it translated--and did not need to rely on any technology other than his eyes and grasp of archaic phraseology.

Captain William Kidd's 315 year old commission from the King of England

Similarly, but on a much more localized scale, I have been working with a client to recreate the land ownership pattern of portions of southwest Washington based on a digital scan of a hard copy map that was produced in 1891. This 120 year old map was created by hand with pen and ink, but it is remarkably accurate given the limitations of surveying and cartographic technologies available at the time. But similarly to Zacks, all we need to do is use our eyes to interpret the map and determine what was happening on the landscape back in the 19th century.

Let's contrast that with the current situation. Most of the maps we create are transmitted as PDFs, JPGs, or some other electronic format, and rarely printed out (maybe 5-10% are printed out). When they are printed, most of the non-profit organizations and government agencies do not have any clear system for cataloging and archiving the maps (or data used to create them) for posterity. Compounding the problem, more and more maps are completely web-based: the base layers might come from a variety of sources--Google, USGS, NOAA, NRCS, you name it--and the 'value-added' content might be coming from any number of other servers. The various layers are widely distributed across dozens of servers, and the underlying information is updated at varying intervals. How do you even capture a "snapshot" of an interactive map like that? What are the chances that the full functionality of any web map can be reproduced 120 years from now? I think very slim indeed, but perhaps I am being overly pessimistic.

The great irony seems to be that we now have access to more information than any other generation in history, but future historians will be able to access only a tiny fraction of it, because we are not doing a sufficient job of preserving it.

Obviously I am not the first person to surf this particular brainwave--for example, see here, here, here, here, and especially here.

Promoting Geographic Literacy

I volunteer on the board of my son's Parent-Teacher-Student Association board. My role is to maintain and update the PTSA's website, but at a recent meeting one of the board members mentioned needing to find grant money to provide world maps to several classrooms in the school. My first thought was "How could it be possible that any classroom in any school lacks something as fundamental to a decent education as a world map?!?" My second thought was "Hey, I have a color plotter, and know a bit about maps..." and before I realized what I was saying had volunteered to provide all of the maps as a donation to the school.

I love designing maps and it would have been fun to create a world map from scratch; unfortunately, I did not have time for such a monumental undertaking, so decided to search for a decent, public domain map. I found one here at the World Factbook.

So far I have provided eight poster-sized versions of the map, and they seem to be a hit with the teachers and the students.

A couple of future world travelers in front of the printed map.

More Historic Mapping--Mt. St. Helens

For over a year I have been working on a series of maps featuring Mt. St. Helens (MSH) and the surrounding region for both the Sierra Club and the National Parks Conservation Association. Both groups have been advocating some major changes to the management status of the current National Volcanic Monument (NVM), and the mapping has been used to support their lobbying efforts.

An interesting spin-off of this work is the recreation of historic land ownership patterns. In order to fully understand the current land ownership and management situation in and around MSH, it's important to have an understanding of the previous policy decisions that got us here. I have been working with Charlie Raines to develop a variety of data from historic maps (100 to 130 years before the present day) and it is really fascinating.

On a personal level, it is humbling to work with these maps that were created by hand--with pen, ink and paper--before there were aerial photographs, orthophotos, satellites, even NAD 27! These old maps georeference remarkably well with the modern-day USPLS townships and sections.

However, there have been some major changes to this landscape over the past 100 years, both natural and man-made. Mt St Helens lost over 1,300 feet of elevation as a result of the 1980 eruption, and we humans built roads, railroads, and numerous large reservoirs on the Lewis, Cowlitz, Nisqually, Bumping, and Columbia river systems. As part of the historic mapping process, I've had a lot of fun 'reversing' these changes by deleting the reservoirs, re-drawing the rivers in their original channels, and erasing highways and interstates.

These maps are still a work in progress so I cannot share them just yet, but here are a couple of screen shots to give you a feel of the historic/modern juxtaposition.

A "split-screen" view, showing an 1891 Northern Pacific Railroad land grant map on the left, and the modern CORE GIS map on the right. Note the fold in the historic map running right-to-left between the 'river' label on the left and Swift Reservoir on the right. Click on thumbnail to embiggen.

Another view of the Northern Pacific Railroad land grant map, this one focused on the region around Mossyrock.

Modern-day view of the same extent.

Hiking Washington's History

Last year I worked on a series of 51 black and white maps for author Judy Bentley's book Hiking Washington's History.I received my copy in the mail today, and it looks great! The published size of the maps is a bit smaller than the versions I produced, so some of the text is a bit difficult to read, but on balance I'm quite happy with the finished product.

In a future post, I'll write about the unique challenges associated with black and white cartography.

Click on images to embiggen.