GDAL学习

GDAL is a C++ translator library for more than 200 raster and vector geospatial data formats. It is released under an X/MIT style Open Source license by the Open Source Geospatial Foundation. As a library, it presents a single raster abstract data model and single vector abstract data model to the calling application for all supported formats. It also comes with a variety of useful command line utilities for data translation and processing. It offers an API for a variety of languages such as C, C++, Python, Perl, C# and Java

The related OGR library (OGR Simple Features Library), which is part of the GDAL source tree, provides a similar ability for simple features vector graphics data.

GDAL 是 Geospatial Data Abstraction Library 的缩写, 最开始的时候是一个用来处理栅格空间数据的类库,OGR 则是则是来处理矢量数据的。后来,这两个库合并成为合并成为一个,在下载安装的时候,都是使用GDAL 这一个名字。

由于 GDAL 对多种栅格数据格式都提供了支持,很多软件都使用它作为底层数据处理的库。这其中比较有名的有:ArcGIS、Google Earth、OpenEV、GRASS GIS、OSSIM、Quantum GIS、MapServer、World Wind.

Core features
- Reading and writing of raster and vector geospatial formats 读写矢量和栅格地理空间数据
- Data format translation 数据格式转换
- Geospatial processing: subsetting, image warping, reprojection, mosaicing, tiling, DEM processing 地理空间数据处理：裁剪投影镶嵌等

Implemented Standards

Catalogue Service for the Web (CSW)
Geographic JSON (GeoJSON)
Georeferenced Tagged Image File Format (GeoTIFF)
Geography Markup Language (GML)
Keyhole Markup Language (KML)
OpenStreetMap (OSM)
Simple Features for SQL (SFSQL)
Web Coverage Service (WCS)
Web Feature Service (WFS)
Well-Known Binary (WKB)
Well-Known Text (WKT)
Web Map Service (WMS)
Web Map Tile Service (WMTS)

读取矢量shp案例：

import sys
try:
    from osgeo import ogr, osr, gdal
except:
    sys.exit('ERROR: cannot find GDAL/OGR modules')
     
# try:
#     from osgeo import ogr
# except:
#     import ogr
 
driver = ogr.GetDriverByName('ESRI Shapefile')
filename='D:/ArcGIS Data/Chinacity.shp'
dataSource = driver.Open(filename,0)
if dataSource is None:
    print('could not open')
    sys.exit(1)
print('done')
layer = dataSource.GetLayer(0)
n = layer.GetFeatureCount()
print(n)
 
extent = layer.GetExtent()
print('extent:', extent)
print('ul:', extent[0], extent[3])
print('lr:', extent[1], extent[2])