Thursday, March 31, 2005
Wednesday, March 23, 2005
Digital Map Publishing
Digital Map Publishing is the expansive title given to a review of ArcReader as a publishing platform in Geospatial Solutions March 2005 issue by Dr Grant Ian Thrall of The University of Florida (Go Gators!) Good review, well written, but the message I took away was what a digital map publisher really wants is GeoPDF! Don't take my word for it, read the article, especially considering the first four paragraphs. More on this later.
GeoPDF Map Gallery
Monday, March 21, 2005
GeoPDF Hacks: Georegistering UTM Maps with Transverse Mercator
The Universal Transverse Mercator system is a widely-used grid system, and its enthusiasts have pushed its use beyond limits placed upon its specification. There are plenty of maps that represent areas that lie in one UTM zone by projecting them in some other zone. Often, this is an adjacent zone, but not always. The MAP2PDF plugin can be cantakerous if you try to use UTM as the map coordinate system for maps that do not lie cleanly in the appropriate zone. What to do? What I do is drop back and punt the UTM (menu selection, not system) for Transverse Mercator. Here's how to do it:
- Pick Transverse Mercator for your map coordinate system
- Take the UTM zone you want and multiply it by 6. E.g., Zone 16 gets you 96.
- Subtract 183 from the result. Zone 16: 96 - 183 = -87
- Enter that value for Central Meridian
- Enter 500000 for False Easting
- If the map is in the Northern Hemisphere, enter 0 for False Northing, else enter 10000000 (ten million)
- Enter 0.9996 for your scale factor
- Georegister as normal
Friday, March 18, 2005
GeoPDF White Paper
Lat/Lon to UTM with Python
Thursday, March 17, 2005
More Google Maps Stuff
A slight technical glitch has nuked our links section. I thought I'd start recreating them over lunch. I didn't remember the URL for Perry-Castañeda Library Map Collection, so I googled
texas maps. Up pops images of Texas maps! Pretty historical maps! Nifty. Works for
california maps, but not for
georgia maps, dadgummit. The search was not in vain, however. I discovered The Hargrett Library Rare Map Collection at UGA.
Blog & Web Updates
Web Guru here, I have changed the look of the blog and will try to make some customizations in the near future. Also, I will post when updates are made on the Website.
-"concert" T's are a great idea!
LGI Tradeshow Update
The Future of GeoPDF
The market for mobile locative technologies is exploding, and I expect to see exponential growth in coming years. A friend wondered what role GeoPDF would play in this future, especially with dramatic increases in wireless bandwidth. Might GeoPDF be rendered quaint by the technologies that lie under things like google maps?
In a word, no.
There are critical roles that simply are not addressed by these technologies. Two that spring immediately to mind are grab-and-go and archiving.
My parents, sister, her family, and many friends from childhood live in Pensacola -- the place I grew up. Hurricane Ivan hit Pensacola and the Gulf Coast pretty hard, and, like thousands of other people, my folks were without power for days. Those guys busting chops overtime in the bucket trucks need stuff they can rely upon whether the net is up or not. As bad as it was for the Pensacola, the folks in and around the Indian Ocean had it much worse. In light of these disasters, what would having current snapshots of entire utilities networks distributed on laptops mean for reliability for stability for utilities? Seems like a no brainer, to me. First responders will need grab-and-go for decades. Warfighters will need grab-and-go for decades. But grab-and-go doesn't have to be strictly serious. Heck, I could see someone developing a grab-and-go GeoPDF app for geocaching. The possibilities are endless.
Anyone in AEC is familiar with as-builts -- documents of record that describe in technical detail how something was built -- and permitting. CAD systems are powerful design tools, but are too expensive and complicated to foist upon the owner and the much broader audience of people who would like to review the as-builts and permits. Plus, they don't readily provide facilities for tabular data (spreadsheets) and supporting documentation. This is likewise true of even the so-called free viewers. In addition, some things need to be published in a specified way with certitude. PDF, and thus GeoPDF, was designed with this as foremost consideration.
John Warnock envisioned PDF's role in both grab-and-go and archiving more than a decade ago in his The Camelot Project [PDF]:
One obvious application for the IPS viewer is in its use in electronic mail systems. Imagine being able to send full text and graphics documents (newspapers, magazine articles, technical manuals etc.) over electronic mail distribution networks. These documents could be viewed on any machine and any selected document could be printed locally. This capability would truly change the way information is managed. Large centrally maintained databases of documents could be accessed remotely and selectively printed remotely. This would save millions of dollars in document inventory costs.
Specific large visual data bases like the value-line stock charts, encyclopedias, atlases, Military maps, Service Manuals, Time-Life Books etc. could be shipped on CD-ROM's with a viewer. This would allow full publication (text, graphics, images and all) to be viewed and printed across a very large base of machines.
Hmmm... combining grab-and-go with archiving of current snapshots, and distributing that data through out your enterprise. Good idea? Good idea!
As I wrap this up, there is one more role that springs to mind: hacking. I just like messing with maps. When something happens in the world, I like to snarf the appropriate map, georegister it, and play around. How far is is from here to there? What's the latitude, Kenneth? Playing around with maps in this way leads to nifty ideas.
GeoPDF is going to be with us, in some form or another, for a good long while, methinks!
Tuesday, March 15, 2005
Maps from the USGS
The USGS is a great source of beautiful and interesting maps. The main entry into USGS maps is a collection of links to other resources, including maps of other planets. USGS Publications Maps gets you closer to USGS maps. Omnia USGS Geology in partes tres, divisa est: Eastern Region, Central Region, and Western Region. The Western Region has nice entry point to their maps, as does the Central Region. If anyone knows about a similar collection for the Eastern Region, please let me know.
One of the key abstractions we use is that we consider three coordinate systems: PDF, projection, and geodetic. From the publishing perspective, we assume that the georegistrant (georegistor?) knows the projection, parameters and datum used to create the map. Given that, we can do inverse projections, datum shifts, whatever. However, we don't worry about any of that during georegistration. All we're doing is registering two two-dimensional Cartesian coordinate systems*. For a wide variety of maps, and nearly all working maps produced today, this works well. However, you start to run into trouble with scanned images, sketchy underlying landbases, etc. One thing we don't do is munge the image, or the graphical representation of the map. So, what we're going to provide is a way to munge the linear mapping between the PDF and projection coordinate systems, via a multi-point georegistration process. We've played around with this internally, and I hope we can get it to you, soon.
* As I hinted in a previous post, georegistration is slightly preferable to georeference in this context, IMHO. Let me know what you think.
Friday, March 11, 2005
Blogger comments kinda working
Aetherial internet types (thanks!) report that they can now open the comments dialog (leave a comment, too, next time!). I've confirmed it. Blogger's status page has the problem as top priority, but doesn't report it as fixed. Try a comment, and if it doesn't work, drop back, and punt.
Blogger comments not working
There is a problem with comment system on Blogger that's preventing folks from posting comments. We want your comments. We love your comments. Keep 'em coming! For now, please send comments to:
geopdf [at] layton-graphics.com
UPDATE: Email from blogger says they're on it. Stay tuned. And now, for something completely different:
The concern for man and his destiny must always be the chief interest of all technical effort. Never forget it between your diagrams and equations. -- Albert Einstein
... and our maps and emacs.
Toughbook + Plugin = Cool Hack
Rich at Mapping Hacks said this:
One of the more interesting bits of information from that post is that Toughbooks are available on ebay for $150. Those are great computers. I remember Matt Westervelt and Terry talking about their Toughbook fights when we were at Etech in 2002...any computer you can fight with is 'da bomb.'
in reference to a hack that Larry, one of our guys at LGI came up with for bass fishing:
- Get Toughbook on ebay for $150
- Get Acrobat and GeoPDF plugin
- Connect Toughbook to GPS
- Georegister chart
- Go fishing
- Put annotations on all the sweet spots
No wonder Larry went on vacation after we shipped...
Get your Mapping Hacks On!
A Mapping Hacks is a cool blog run by a team of geohackers dedicated all things mapping. Check 'em out.
Wednesday, March 09, 2005
PDF to Google
While Lance and I were checking out his latest cut of a dialog for multi-point georegistration, JB hacked his plug-in source to kick off a Google maps search based upon the current cursor position in a GeoPDF. Oh, to see the reaction when the Google map came up dead on. JB's a believer now. No reason we couldn't do it for Topozone, TerraServer, MS TerraServer... you name it.
Getting Longitudes and Latitudes with Google Maps: Why?
A friend asked (post a comment next time!) what the point of the Getting Longitudes and Latitudes with Google Maps was, and without any context, I can see how this might be confusing. My bad. Here's why I think it's a handy trick.
In order to create a GeoPDF with the MAP2PDF for Acrobat plug-in, you have to know the locations and coordinate values of two points the map you're georegistering (known also as georeferencing (Why we call it georegister is a discourse in pedantics better left to another time... (Yes, I hack lisp.))). The GeoPDF creation process in brief:
- Open map in Acrobat
- Click on the GeoRegister button
- Click on the Map Coordinates button
- Pick your projection from the list (more on this later) and OK
- Click Registration Points
- Click on two points on map and enter corresponding longitudes and latitudes, or map coordinate values and OK
- Click OK
That's it. Experience has shown that one of the tricky bits can be getting the longitudes and latitudes of known points -- an that's where Google maps comes in. But first, let me address the "more on this later" of picking a projection. For many maps of practical interest, the differences between how different projections represent the same area may be tolerably small. When playing around with different maps of dubious pedigree, we've used Lambert Conformal Conic or Transverse Mercator, and have found that just using the default values often does a good job. What's a good job? Patrick rounded up an Atlanta road map from who knows where that contained no projection information at all, and georegistered it using the process described here. He's got the Acrobat and the plug-in on a laptop with GPS, and one of his favorite tricks is to turn on GPS tracking while driving -- showing his location on the laptop as he goes. When you stop for a red light, the icon is at right intersection and on the road. You're traveling South on I75, the icon is on the Southbound side, etc. The point is not that this is possible -- plenty of navigation systems out there, -- but that he was able to whip one up on his own quickly, easily, and without knowing the first thing about the origin of the map.
While many maps provide a graticule (lines of longitude and latitude drawn on the map) or a grid of map coordinates from which it is easy to extract real world coordinates for the point you're looking at. But street maps often do not present such data. The nice thing about the Google hack is, you can just enter a street address or an intersection and voila! -- your coordinates have arrived.
Tuesday, March 08, 2005
Getting Longitudes and Latitudes with Google Maps
Google Maps is pretty slick. Double-clicking a point in a Google map centers the map on the double-clicked point. You can zoom in using the "zoomer bar" to the left, and double-click again to get a better hit on your point. If you click the link to this page to the upper right, you should see something like:
I'm not sure which latitude and longitude that is -- WGS84 at zero elevation? I need to check.
The sample point is an Atlanta landmark -- The Varsity.
UPDATE: JB's hack makes it look like the coordinates are either WGS84 or NAD83.