warp-sabre is a suite of programs to generate calibrated slippy map tiles from a variety of old maps, and the main program to generate the in-house mapping at SABRE Maps (https://www.sabre-roads.org.uk/maps). It is derived off a suite of OpenStreetMap tools called warp-gbos (that was used to produce the New Popular and Seventh Series tiles there, that pre-date SABRE Maps) with some extra bells and whistles to handle archaic things such as the MOT maps. ==Features== The suite currently supports the following: Ordnance Survey GB National Grid WGS84 Lat/Lon Cassini (as used on England and Wales MoT maps) Scottish Bonne (as used on Scottish MoT maps) It does not currently support (but will in the future): Ordnance Survey GB National Yard Grid (but conversion can be done manually) Irish Grid as used on OSI and OSNI mapping OSGB36 Lat/Lon ==Programs== warp-sabre - combines a map image and calibration file to create a rectified map image and a Keyhole Markup Language (KML) file that can be loaded into Google Maps or Google Earth to check the accuracy of the calibration file gentiles - takes a group of rectified map images, with KML files, and creates all the tiles (may take hours, sometimes days, to run) cleartiles - takes a group of rectified map images, with KML files, and deletes all the associated tiles. This is important when doing small, incremental updates to a set of tiles with multiple maps; running cleartiles before gentiles makes sure that all tiles that need to be updated (particularly those that span the edge of maps) are re-created, but others are left alone. ==Calibration file format== Calibration files are a series of comma separated values. Each co-ordinate is on one line. They look slightly different depending on whether you are using lat / lon or grid references. ===Latitude / longitude=== A lat / lon file looks something like this: p,51.8,-0.5,300,200 p,51.8,-0.1,1200,200 p,51.7,-0.5,300,900 p,51.7,-0.1,1200,200 The "p" tells the calibrator this is a lat / lon co-ordinate. The next values are the latitude and longitude of the point, followed by the x and y co-ordinate the point is on the map image. ===Grid reference=== A grid reference file looks something like this: os,400000:250000,300,200 os,500000:250000,1200,200 os,400000:150000,300,900 os,500000:150000,1200,200 The "os" tells the calibrator this is a grid reference co-ordinate. The next values are the metres east and metres north of the grid reference, followed by the x and y co-ordinate the point is on the map image. (Note, the grid reference values are separated by a colon, not a comma; this is because grid references can also be specified using the two letters + number format, which is not generally used by SABRE Maps). In both of the examples, the calibration defines the four corners of a map - top left, top right, bottom left and bottom right. The four corner co-ordinates are the most important ones to include in a calibration file, otherwise the map has no idea where it is supposed to be displayed in the world - at all. For information on how calibration files work, see : https://www.sabre-roads.org.uk/wiki/?title=SABRE_Maps/Calibrating