In addition to its primary function in retrieving, displaying and exporting TerraServer imagery like USGS topo maps and aerial imagery, USAPhotoMaps has some handy additional capabilities. I’ll talk about the GPS functions in another post, but here are some other useful functions available in USAPhotoMaps:
Archive for July, 2007
DialDirections is a new cellphone service where you:
1. Call their number 347-328-4667 (spells DIR-ECT-IONS)
2. Speak your current street intersection, and where you want to go (address, street intersection or chain store name)
3. Get back directions to your desired destination via a text message.
“Available in the greater metro areas of San Francisco, New York City and Los Angeles”; additional metro areas coming in the future. Free except for your cellphone service’s standard charges, which for many plans will be zero.
Tom Patterson is a cartographer with the US National Park Service, and runs the Shaded Relief website, with many articles, tutorials and links related to terrain shading techniques in cartography. But he has also created fantastic terrain and landcover imagery and data, all of which is freely downloadable, license-free and reproducible in any format. These would make great background imagery for national and world maps created using GIS software. Some of the files are very large (well over 100 MB in size), so downloading them may take a while depending on your connection speed.
Continue reading ‘US/Global Terrain Shading Data And Landcover Imagery’
SlashGeo has a post up asking for feedback and info about the various version of SRTM-90 data. SRTM was the Shuttle Radar Topography Mission, an instrument package aboard a 2000 flight of the Endeavour space shuttle that mapped the earth’s topography at a resolution of 30 meters using radar. While one of the most inclusive and comprehensive worldwide topographic datasets, SRTM has a few drawbacks:
- The original data had many voids, holes and other irregularities
- The SRTM radar registered buildings and vegetation as terrain, and added their height to the actual terrain height
- Radar mapping has problems with dry sand (e.g. sand dunes)
- 30-meter data has only been released for the US; for the rest of the world, the 30-meter data was re-sampled to 90 meters (hence, SRTM-90)
NASA has released SRTM Version 2, a “cleaned-up” version of the original SRTM data with holes and voids filled, and the data irregularities supposedly cleaned up; this data is available from the USGS Seamless Server. There are still problems with this cleaned data, like the mountain I viewed in Mexico that had a hole in its summit that went all the way down to sea level. I’ve been using my own version of SRTM-90, with holes in the original data patched using GTOPO30 data. But since GTOPO30 data has a resolution of 1 km, my solution was less than ideal.
The SlashGeo post and comments mention two attractive-sounding alternative versions of SRTM-90 data:
- The CGIAR Consortium For Spatial Information has released Version 3 of their cleaned-up SRTM-90 data, using contour interpolation and alternate data sources to fix voids and holes. I looked at CGIAR’s Version 2 before, and wasn’t satisfied with it. I’ve taken a cursory look at some of their Version 3 compared to NASA’s Version 2, and while the CGIAR data still isn’t perfect, it looks better than the NASA Version 2 data (and also better than my patched data). But be prepared to have the downloads timeout on you, as happened to me on multiple occasions on the main site (haven’t tried the mirror download sites yet). There’s also a Google Earth file that offers a more convenient interface for viewing and downloading the data.
- The USGS has developed their own “cleaned-up” version of the SRTM-90 data for use with the WWF’s HydroSHEDs program. Haven’t looked at these yet, but more information and download links are available from their website (I wasn’t able to successfully download any data - curse you, ArcIMS). Also, data is currently only available for Central and South America, a small part of the US, and parts of Asia and Oceania.
USAPhotoMaps offers a convenient and easy interface to TerraServer imagery (USGS topo maps, aerial photography). But it’s still a pain to have to sit and wait for imagery to be downloaded for a selected area you haven’t looked at before, since the data for that area can’t be permanently cached on the hard drive until it’s downloaded. If there’s a geographical area that you know you’ll want to have data “on call” for, there’s a free utility that will pre-cache TerraServer image data from that area on your hard drive for fast future access and retrieval by USAPhotoMaps.
Continue reading ‘Caching TerraServer Imagery For USAPhotoMaps’
An earlier post described TerraClient, a program that lets you download large-area full-resolution USGS aerial photo imagery from the TerraServer website. That’s more convenient than downloading individual pieces from the USGS Seamless Server and then stitching them together, and has the additional advantage of letting you see the areas you’re selecting for download on-the-fly. But it has the disadvantage of producing images that aren’t “georeferenced”, i.e. they don’t come with the coordinate information needed to import and use them directly into a GIS viewer or editor.
There’s a free program called USAPhotoMaps that can create georeferenced TerraServer imagery for smaller geographic areas than TerraClient, and not just black-and-white aerial photos: it can also export georeferenced seamless color USGS topographic maps and high-resolution (0.15 to .65 meter) color aerial photos from selected urban areas. USAPhotoMaps has a far friendlier and faster interface than the USGS Seamless Server (which also offers this imagery in georeferenced format), and USAPhotoMaps has a bunch of additionalcapabilities that are easy and convenient to use. This post will deal with using TerraServer to view and export TerraServer imagery; its additional capabilities will be covered in future posts.
Continue reading ‘Georeferenced TerraServer Imagery With USAPhotoMaps’
Got an email from 192.com, a UK mapping website, announcing some new enhancements to the site:
- Ordnance Survey Maps with all streets labeled
- 12.5-cm resolution aerial photography
- Journey planner
The interface is Flash, proprietary and a bit small in size, but useable. I’ll defer to any UK readers as to the quality of the OS maps, but the aerial photography is very impressive. Here’s shot of Stonehenge at maximum zoom, clearly showing individual visitors:
Note: There’s no separate settings for maps or aerial photography. As you zoom in, you first get OS Maps, and when you zoom in very close, it switches over to aerial photography. I tried three locations at random in the UK, and they all had high-res aerial imagery, so I’ll believe their claim that it covers the entire country.
192.com has other mapping service features, like people and address search, business search, local search, etc.. Doesn’t have all the capabilities of Google Maps, but the OS Maps and high-res aerial photography could make this a useful alternative to GM for UK residents.
Among the highest quality DEM data you can get to go with a standard USGS 1:24K topo map is 10-meter SDTS DEM data, with heights specified to the nearest 0.1 meters (though the altitude accuracy of the DEM likely doesn’t warrant that resolution). I find it superior to the 10-meter NED data provided by the USGS Seamless Server, with fewer artifacts, although the SDTS format isn’t as well-supported as the DEM formats available at the Seamless Server. The SDTS DEMs are also in UTM NAD27, same as typical for USGS topo maps, versus the geographic projection for Seamless Server DEMs. There are a fair number of pay sites on the Web that offer these SDTS DEM files for a price, but there are also two locations where you can download them for free:
- The GIS Data Depot has gone through some changes over the years, but is still around. It offers not just SDTS DEMs but a host of other GIS data, some free, other not free (you can often find the paid data for free elsewhere on the web). Data is classified as “statewide” or “countywide”, and you’ll find the SDTS DEMs in the “countywide” sections, listed in the Digital Elevation Models (DEM) - 24K section under the 1:24K topo map name whose area they cover (offered in both 10-meter and 30-meter resolutions) . The catch with the free “Normal” downloads is that they are at slower speeds than the paid “Premium” download (appears to be roughly 10 kilobytes per second or so).
- The ATDI SDTS data page offers only 10-meter SDTS DEMs, with a more basic interface but at higher download speeds. Enter the latitude and longitude of the location you’re interested in, and you’ll get a download link to the 10-meter SDTS DEM datafile for that location, along with the name of the USGS 1:24K topo map that corresponds to the area covered by this DEM.
