Sunday, April 24, 2011

The US National Map

Earlier this month the US Geological Survey (USGS) released their latest version of The National Map Viewer.

US National Map View of Maumee, Ohio

The same view of Maumee, Ohio with the aerial image
background turned on

The US National Map is not a map per se.  You can't ring up the USGS and say "Send me a copy of the National Map."  It doesn't exist as a single product.  The US National Map is a collection of digital geographic and geospatial data that, when brought together, forms the foundational map of the United States.  Here's how the USGS describes it:

"As one of the cornerstones of the U.S. Geological Survey's (USGS) National Geospatial Program, The National Map is a collaborative effort among the USGS and other Federal, State, and local partners to improve and deliver topographic information for the Nation. It has many uses ranging from recreation to scientific analysis to emergency response. The National Map is easily accessible for display on the Web, as products and services, and as downloadable data. The geographic information available from The National Mapincludes orthoimagery (aerial photographs), elevation, geographic names, hydrography, boundaries, transportation, structures, and land cover. Other types of geographic information can be added within the viewer or brought in with The National Map data into a Geographic Information System to create specific types of maps or map views. The National Map is a significant contribution to the National Spatial Data Infrastructure (NSDI) and currently is being transformed to better serve the geospatial community by providing high quality, integrated geospatial data and improved products and services including new generation digital topographic maps."

OK, like I said, it's a collection of digital geographic and geospatial data that forms the foundational map of the US.  Geeze, I think government bureaucrats get paid by the word.

Here is the USGS's introduction to the National Map program and the National Map Viewer:

The National Map Viewer is the USGS's on-line portal to all the data that makes up the National Map.

The Viewer is pretty good (if you are at all interested, it is built on ESRI's ArcGIS Server technology) and offers some neat functionality.  It will provide location information in a number of formats, including US National Grid coordinates, it has a pretty robust reverse geocoding feature (click on a building on the map and the map returns the street address for that location) and it will provide spot elevations from the national elevation dataset.  You can do area and distance measurements, add text and simple graphics and even add data from external sources like a GoogleEarth KML file or a web mapping service.  You can also bring up indexes for the USGS's standard map products like the US Topo series of maps and link to them for download as GeoPDF files.  For advanced users the Viewer offers some pretty good search and query builder functionality, so you can find specific data that is embedded in the data layers.

There are some shortcomings, however.  The print function is essentially useless and is perhaps THE major drawback of this Viewer.  About all it does is grab a screen shot of your viewer and dumps it to a PDF file.  The USGS needs to wake up and realize that people still want quality paper maps and with today's technology it should be easy to print a fully detailed paper map with things like a grid, scale indicator, geographic extents, legend, etc.

The Viewer also exhibits a common issue found in web-based maps - map content naming conventions can be pretty obtuse and downright confusing.  While the Viewer does pretty good with the base data layer naming conventions, when you start using advanced features like the Query Builder you start to interact directly with the database field names.  For example, if I'm building a query to identify all the wetlands in my county I'm presented with a list of 'Columns' (which are the database field names).  Those column names are confusing and don't mean anything to most humans.  We get to pick from selections named 'ATTRIBUTE' or 'OBJECTID' or 'SHAPE_Area'.  There is an easy solution to this - the GIS professional building this map can establish what are called 'field alias' names - a human-friendly nickname for each of the information fields.  ATTRIBUTE can be displayed as 'Wetland Attribute', OBJECTID can be displayed as 'Wetland ID' and SHAPE_Area can be displayed as 'Wetland Area'.  This naming convention issue usually reflects the fact that GIS professionals with little cartography experience compiled the data for use in the Viewer.  (If I seem to be nit-picking here it is because I build maps for a living using this same technology.  I know these are issues that are easy to fix and should have been taken care of before the Viewer was opened up to the public.)

These shortcomings aside, the National Map Viewer is pretty darned good.  I'd say the USGS gets a good solid 'B' for this effort.  If they'd improve the damned printing issue I'd give them an 'A'.


Saturday, April 23, 2011

Which Way North - Evaluating the Compass

It's been a while since we looked at the merits and shortcomings of specific compass designs.  Over the past six months or so I've been testing and evaluating a number of handheld compasses from various manufacturers.  It has been something of a grail quest, searching for the perfect compass.  Along the way I've learned a lot about compass design, accuracy and usability.  In the next series of postings we'll discuss specific compasses and perhaps help you select a compass for your needs.  Not all of what I evaluated were modern compasses; I've included a few examples in this evaluation that were manufactured over 60 years ago and represent designs that go back over 100 years.

Before we get started let me state that there is no such thing as the perfect compass.  No one design can meet all needs.  The best approach in compass selection is to pick the design that best meets the needs of the job at hand.  If you are running an orienteering course you'll probably want to pick a compass specifically designed for that sport.  However, if you are doing serious backwoods land navigation you'll want a direct reading compass that can give accurate azimuths to within 1/2 of a degree.  On the other hand, if you are a geologist doing stratigraphic mapping you'll need a compass that will also allow you to measure the strike and dip of rock formations.  Always pick the tool that best suits the task at hand.

Over the next series of postings in the Which Way North series I'll evaluate specific compasses on the following criteria:

1. Basic Design - How good is the basic design of the compass, particularly if the compass was designed for a specific function?  How well does the design meet the stated goal?

2. Features - Are any added features (luminous markings, baseplate scale markings, built-in clinometers, etc.) useful and do they add to the functionality of the compass?

3. Execution - Did the manufacturer do a good job building the compass?

4. Usability - How easy is it to use the particular compass in the real world?

6. Accuracy - How accurate is the compass (in degrees) when used as it was designed and intended to be used?

Much of this evaluation will be subjective.  After all, it is my blog so I set the rules.  However, my subjective evaluation is based on over 40 years of compass use as a geologist, topographer and Army engineer officer.  I may be a bit subjective in my evaluation, but it is a well honed subjectivity.

Other things you should understand about my evaluation criteria are:

1. I value accuracy above all else.  If a compass is not accurate (within it's design parameters) then it is a piece of junk.  I don't care who made it or how expensive it was, if it ain't accurate it's junk.  I think it is important to understand how I evaluate accuracy.  I have access to an azimuth station where I test all my compasses for accuracy.  An azimuth station is a site where survey points have been established and the precise azimuths between points (in relation to true north) is established.  Each compass is checked against three points each roughly 90 degrees apart.  All are checked for handheld accuracy and if possible, supported accuracy when mounted on a jacob staff.  Each compass is tested three times in each mode and the magnetic azimuth results averaged.  The averaged result is then adjusted for local declination (as determined by NOAA) and checked against the known azimuths between each of the survey points.  The difference between the surveyed azimuth and the adjusted magnetic azimuth is the compass accuracy.

2. Ruggedness of design is next on my list of criteria.  A compass that is marketed for outdoor use should be able to withstand that use and deliver reliable and accurate service.  I'm not saying that we should expect to use a compass as a substitute hammer, but it is not unreasonable to expect a land navigation compass to easily withstand the normal bumps and shakes that come with being used out of doors.

3. Declination.  A lot of compasses have adjustable declination scales.  I do not consider the presence or absence of an adjustable declination scale of any particular importance.  In my opinion adjusting for declination on the compass gives a false sense of security.  There are far too many variables in the declination equation to allow it to be handled by a coarse declination scale built into a handheld compass.  However, an adjustable declination scale can be useful for another purpose - adjusting out any error built into a particular compass or compass design.

4. You rarely use the compass all by itself so consider it part of a land navigation kit.  This kit should also include maps of the area you are working in, a plotting scale and a notebook and pencil.  All my evaluations are done in consideration of the compass as part of this kit.

Also keep in mind that I didn't test every compass available.  My schedule (and wallet) won't allow that.  However, I did obtain the most common examples available from the major manufacturers like Silva, Suunto, Brunton, K&R and a few others.  If you have interest in a particular model or style let me know.  I may already have it on my list for evaluation or may be able to get an example to test.

So stay tuned for the plain truth on compasses!


Friday, April 22, 2011

Terrain Analysis

Last week I stumbled across this gem on YouTube -

It is a slightly dry film put out by the US Geological Survey in 1955 showing the modern (for the time) processes developed for natural resource analysis using aerial photography.

The guy narrating it sounds about as excited by his work as a dry goods salesman discussing the newest laundry soap.  Zzzzzzzzz...

But once past the dry narration I was interested by the methods demonstrated for geological, hydrological, soils and forestry analysis.  What struck me was that these were the precise methods we were taught at the Defense Mapping School as late as the early 1990s.  These photo analysis processes formed the basis for what we called Terrain Analysis, and in fact my job title for much of my Army career was Terrain Analysis Technician (MOS 215D).

This film approaches each type of analysis as an independent process - an end in itself.  We carried the analysis to the next level and merged the output from each of these four disciplines, mixed in some military-specific data like vehicle off-road capabilities, tossed in some road network analysis, some urban analysis and a pinch of weapon systems analysis and produced what we called a military terrain analysis.  Our products were usually delivered in the form of map overlays known as a combined obstacle study.  The process was very labor intensive and usually tightly focused on specific geographic areas like the Fulda Gap in Germany or the Koksan Bowl in Korea, natural movement corridors that had been used by armies for centuries.

Soldiers going into the Army's Terrain Analysis field received extensive training in field identification methods like geological and soils analysis, hydrological analysis and route engineering studies.  They were taught to observe, test and measure in the field using a variety of hands-on methods.  Next they moved to the classroom and were taught advanced aerial photo analysis techniques and applied their field knowledge to what they saw in the photos.  It was hours and hours of peering at photos through stereoscopes, analyzing texture, tone and pattens to develop a detailed analysis of the terrain and it's impacts on military operations.

Computers have taken on the burden of much of this analysis, and today you can feed a digital image into a sophisticated image analysis package like ERDAS Imagine and have it analyze huge swaths of territory in a small fraction of the time it took using the old manual methods shown in the film.  Still, it is fun to see how things were done in the good old days when men were men, hardhats were made out of aluminum and the science of aerial photo analysis found new applications in the civilian and military worlds.