Global Differential GPS uses a large ground network of real-time reference receivers, innovative network architecture, and real-time data processing software, the GDGPS System provides sub-10 cm positioning accuracy and sub-nanosecond time transfer accuracy anywhere in the world, on the ground, in the air, and in space, independent of local infrastructure.
Tag: mapping
Facebook and OSM
The OSM global copy receives up to 5M changes every day, which means our local copy would quickly become outdated if we didn’t regularly update it. To reduce the risk of bad edits, whether intentional (vandalism) or unintentional, we don’t update our local copy directly. Instead, changes between the 2 versions are reviewed and accepted into the local copy. This all needs to be done on a regular cadence, or the growing difference between the global and local versions will require significant time and effort to catch up. We developed 2 new tools to help us keep pace: Logical changesets (LoChas) and our new machine-augmented automatic review system (MaRS).
LoChas break OSM changesets into individual CRUD operations and then cluster them for more efficient human review. MaRS uses a blend of heuristics and machine learning (ML) techniques to automate evaluation of LoChas that don’t require a further nuanced review. The ultimate goal of these tools is to create a funnel where machine-augmented techniques reduce the workload that requires human intervention.
Space Radar
Capella’s high revisit x-band constellation with InSAR capability will capture millimeter-scale change’s on the Earth’s surface. Interferometric synthetic aperture radar is a radar technique used in geodesy and remote sensing. This geodetic method uses 2 or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation, using differences in the phase of the waves returning to the satellite or aircraft. The technique can potentially measure millimeter-scale changes in deformation over spans of days to years. It has applications for geophysical monitoring of natural hazards, for example earthquakes, volcanoes and landslides, and in structural engineering, in particular monitoring of subsidence and structural stability.
Coordinate Precision
Medieval Trade Routes
Even before modern times the Afro-Eurasian world was already well connected. This map depicts the main trading arteries of the high middle ages, just after the decline of the Vikings and before the rise of the Mongols, the Hansa and well before the Portuguese rounded the Cape of Good Hope.
Sloppy Geocoding
MaxMind determined that 1m IP addresses were operated by entities in Pretoria, and so it geolocated those IP addresses to the coordinates offered by the NGA for the city. And any time someone uses one of those IP addresses to do something bad—like cyberbullying the owners of a leather shop—it looks to someone who maps the address like the bad thing is being done by someone sitting in John and Ann’s backyard.
Internal Use Only
Adventures in acquiring satellite imagery
The longest amount of time any area in the continental United States has gone without an update on Google Earth has been 8 years. From 2008 to 2016, a series of dry lake beds in Southwestern Nevada located in the Tonopah Test Range was a blind spot from the all-seeing corporate monolith continuously mapping the Earth. So we bought a satellite image ourselves. We would like to invite you to view image #103001000EBC3C00 yourself. Or — since the image is for internal use only — you can look at a painting of the image online.
NYC Street Tree Map
The NYC Parks department maintains an online map of the city’s street trees — currently 679K mapped trees from 422 different species. Our tree map includes every street tree in New York City as mapped by our TreesCount! 2015 volunteers, and is updated daily by our Forestry team. On the map, trees are represented by circles. The size of the circle represents the diameter of the tree, and the color of the circle reflects its species. You are welcome to browse our entire inventory of trees, or to select an individual tree for more information.
Google Maps name arbiter
The East Cut is a neighborhood in San Francisco invented by a branding agency. Such things usually wither on the local-business bullshit vine, but thanks to Google Maps, it’s now the plain reality of that part of town.
Imaginary cities
A Japanese graphic designer has made it his life’s work to design an improbably realistic and detailed map of a city that doesn’t exist.
Nagomuru City, located in a country called Naira that very closely resembles Japan but isn’t quite the same place, has everything you could want from the city you live in, from house numbers to subways to convenience stores to art colleges to 1970s housing complexes to ancient temples, except the possibly desirable quality of actually existing in 3 dimensions.
Gregor J. Rothfuss 