Google Maps. Launch Google MapsLaunch Maps in LUNA Browser The over 120 historical maps in the Google Maps have been selected by David Rumsey from his collection of more than 150,000 historical maps; in addition, there are a few maps from collections with which he collaborates. These maps can also be seen in the Gallery layer of Google Earth, Rumsey Historical Maps layer, and in the Google Earth viewers on this website. All the maps contain rich information about the past and represent a sampling of time periods (1680 to 1930), scales, and cartographic art, resulting in visual history stories that only old maps can tell. Each map has been georeferenced, thus creating unique digital map images that allow the old maps to appear in their correct places on the modern globe. The original historical maps are first made into digital images by scanning them with high resolution digital cameras.
Processing and hosting of the Rumsey Historical Maps in Google Maps is provided by Geogarage. Africa 1787 - David Rumsey Historical Map Collection. OpenLayers Mongo Search. Geospatial Indexing. This document provides a more in-depth explanation of the internals of MongoDB’s 2d geospatial indexes. This material is not necessary for normal operations or application development but may be useful for troubleshooting and for further understanding. Calculation of Geohash Values for 2d Indexes When you create a geospatial index on legacy coordinate pairs, MongoDB computes geohash values for the coordinate pairs within the specified location range and then indexes the geohash values. To calculate a geohash value, recursively divide a two-dimensional map into quadrants. Then assign each quadrant a two-bit value. For example, a two-bit representation of four quadrants would be: These two-bit values (00, 01, 10, and 11) represent each of the quadrants and all points within each quadrant.
To provide additional precision, continue dividing each quadrant into sub-quadrants. Multi-location Documents for 2d Indexes New in version 2.0: Support for multiple locations in a document. GDAL-OGR, le couteau suisse du géomaticien — GDAL v1.9.0 documentation. GDAL - Geospatial Data Abstraction Library. Professorship in Environmental Informatics at Aalto University.