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Geoapplications development
http://rgeo.wikience.org
Higher School of Economics, Moscow, www.cs.hse.ru
Why do we use maps?2
Pictures from Лебедева О.А., Картографические проекции (методическое пособие), Новосибирский учебно-методический центр по ГИС и ДЗ, Новосибирск, 2000
Map projection (leads to distortions)3
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https://en.wikipedia.org/wiki/Geoid
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Datum: aligning spheroid (ellipsoid)4
Geoid/Earth surfaceSpheroid 1Spheroid 2
Putting all together5
Notes on CRS definition6
select distinct coord_ref_sys_kindfrom epsg_coordinatereferencesystem
Notes on CRS definition (2)7
# R code# Convert (lat, lon) in meters to (lat, lon) in degrees
library(raster)library(rgdal)
# (lon, lat) in UTM projection – units are metersutm_c = cbind(470115, 6322515)utm_sp = SpatialPoints(utm_c, proj4string=CRS("+init=epsg:32637"))utm_sp
# convert to (lon, lat) in WGS84 – units are degressglobal_sp <- spTransform(utm_sp, CRS("+init=epsg:4326"))global_sp
Ellipsoids8
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Datum9
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https://en.wikipedia.org/wiki/Geodetic_datum
https://en.wikipedia.org/wiki/World_Geodetic_System
Coordinate systems (CS)10
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Spherical geographic coordinate system11
° °
° °
Can you port that on Java from C++?http://www.codeproject.com/Articles/15659/Longitude-Latitude-String-Parser-and-Formatter
Cartesian coordinate system12
Cylindrical Transverse Cylindrical Oblique Cylindrical
Secant Cylindrical
Conical Secant Conical Planar Secant Planar
Projections
http%3A%2F%2Fwww.nps.gov%2Fgis%2Fgps%2F04_datums_coordinatesystems_65.ppt
Projections14
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http://www.nps.gov/gis/gps/04_datums_coordinatesystems_65.ppt
Why a map projection matters?15
𝑑 = 𝑥1 − 𝑥2 2 + 𝑦1 − 𝑦2 2
Equirectangular projection17
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•Link 1
The plate carrée (French, for flat square), is the special case where φ1 is zero.
UTM: Universal Transverse Mercator18
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http://www.geo.hunter.cuny.edu/~jochen/GTECH201/Lectures/Lec6concepts/Map%20coordinate%20systems/UTM%20and%20UPS.htm
UTM: Universal Transverse Mercator19
Apply a custom Transverse Mercator projection to each strip (zone)
Pic 1 Pic2 Pic3
UTM: Universal Transverse Mercator20
• Custom means you have a separate cylinder for each strip (zone)
• The cylinder is aligned to cross the spheroid along two lines (in red)
• Each line is 180 km apart from the central meridian of a zone
Pic 1 Pic2 Pic3 Pic4
UTM: zones21
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• International Date Line)•
UTM: zones (another picture)22
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• International Date Line)•
PIC
UTM: N & S23
UTM: False Easting and False Northing
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Link 1
False easting False northing
North zones 500,000 m none
South zones 500,000 m 10,000,000 m
Link 2
False northing – no negative y-coordinates for all locations in southern hemisphere zones (10,000,000 m is enough) False easting – no negative x-coordinates west of a zone's central meridian.
Northern zones do not use false northing: their y-coordinates are naturally positive.
𝒚
𝒙
𝒚
𝒙 = 𝟑𝟎𝟎 𝟎𝟎𝟎 𝒚 = 𝟒 𝟎𝟎𝟎 𝟎𝟎𝟎𝒙 = −𝟐𝟎𝟎 𝟎𝟎𝟎without false easting
UTM: distortion25
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UTM: best practices26
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Link 1
UTM: a limitation27
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Universal Polar Stereographic system28
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Link 1
Military Grid Reference System (MGRS)29
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Military Grid Reference System (MGRS)30
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Link 1
NASA WW Example: MGRS Grid31
MGRS
Sinusoidal projection: very large scenes32
Sinusoidal projection33
http://modis-atmos.gsfc.nasa.gov/MOD04_L2/grids.htmlhttps://en.wikipedia.org/wiki/Sinusoidal_projection
EPSG database: www.epsg.org34
Collection of CRS, CS, datum, etc.
EPSG Dataset v8.7 contains:
5821 coordinate reference systems (CRS)from EPSG:200 to EPSG:69036405
126 coordinate systems (CS), CS != CRS678 datum14 variants of prime meridians4232 CRS transformations
(directly from → to)1829 revisions…..
21 tables
CRS Text Formats35
Try GeoTools, GDALhttp://docs.geotools.org/stable/userguide/library/referencing/crs.htmlhttp://www.gdal.org/gdalsrsinfo.html
GDAL (gdalsrsinfo):• PROJ.4• OGC WKT• XML (GML based)• ESRI WKT format• Mapinfo style CoordSys format• simplified, etc.
http://spatialreference.org/
raro@ubuntu-pelligrini:/mnt/hgfs/RS_DATA/Landsat8/LC81790212015146-SC20150806075046$
gdalinfo ./LC81790212015146LGN00_sr_band1.tif
Driver: GTiff/GeoTIFF
Files: ./LC81790212015146LGN00_sr_band1.tif
Size is 8191, 8271
Coordinate System is:
PROJCS["WGS 84 / UTM zone 37N",
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",39],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
UNIT["metre",1,AUTHORITY["EPSG","9001"]],
AUTHORITY["EPSG","32637"]]
Origin = (224385.000000000000000,6322515.000000000000000)
Pixel Size = (30.000000000000000,-30.000000000000000)
Metadata:
AREA_OR_POINT=Area
Band_1=band 1 surface reflectance
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 224385.000, 6322515.000) ( 34d27'55.58"E, 56d57'49.93"N)
Lower Left ( 224385.000, 6074385.000) ( 34d43' 3.37"E, 54d44'27.51"N)
Upper Right ( 470115.000, 6322515.000) ( 38d30'26.82"E, 57d 2'42.39"N)
Lower Right ( 470115.000, 6074385.000) ( 38d32' 5.80"E, 54d48'56.61"N)
Center ( 347250.000, 6198450.000) ( 36d33'23.03"E, 55d54'25.94"N)
Band 1 Block=8191x1 Type=Int16, ColorInterp=Gray
Description = band 1 surface reflectance
GDAL output in WKT for Landsat 8 Moscow scene
don’t worry due to font size – we are looking closer on it
just in several slides
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http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html
PROJCS["WGS 84 / UTM zone 37N",
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84", 6378137, 298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",39],
PARAMETER["scale_factor",0.9996],
PARAMETER["false_easting",500000],
PARAMETER["false_northing",0],
UNIT["metre",1,AUTHORITY["EPSG","9001"]],
AUTHORITY["EPSG","32637"]]
EPSG codes interpretation37
One of the EPSG goals is to give short codes for frequent combinations to exchange metadata, the below WKT can be replaced by EPSG:32637
<geographic cs><projected cs> UTM 37 North
<prime meridian>
EPSG codes interpretation (2)38
PROJ.439
The "no_defs" item ensures that no defaults are read from the defaults files. Sometimes they cause surprising problems.
http://lists.osgeo.org/pipermail/mapserver-users/2003-November/046863.html
gdalinfo -proj4 LC81790212015146LGN00_sr_band1.tif
+proj=utm +zone=37 +datum=WGS84 +units=m +no_defs
Notes on WGS8440
As you can see from the EPSG database, WGS84 may mean (in different context) different entities:
• Coordinate reference system• Datum• Ellipsoid
Ellipse (1) – ellipsoid (2) – spheroid (3) – oblate spheroid, ellipsoid of revolution, reference ellipsoid, Earth ellipsoid (4)
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Wikipedia: Ellipse Wikipedia: Spheroid
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Wikipedia: Ellipsoid
Ellipse (1) – ellipsoid (2) – spheroid (3) – oblate spheroid, ellipsoid of revolution, reference ellipsoid, Earth ellipsoid (4)
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(2) (3)(4)
SPHEROID["WGS 84", 6378137, 298.257223563,
AUTHORITY["EPSG","7030"]]
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https://en.wikipedia.org/wiki/Earth_ellipsoidhttps://en.wikipedia.org/wiki/Reference_ellipsoid
Reproject (raster=R, targetCRS=CRS, options)43
→ →
Reprojection: the process44
http://demo.geo-solutions.it/share/OptimizingRasterReprojection.pdf
Reproject: visualization in web maps45
Reproject use case: scenes from different projections46
Reproject: mosaic spanning several UTM zones47
http://www.nrcan.gc.ca/earth-sciences/land-surface-vegetation/land-cover/north-american-landcover/9152https://en.wikipedia.org/wiki/Canadian_Arctic_Archipelago
Lambert Conformal Conic (LCC)Ellipsoid Model: WGS84
(original Landsat projection is UTM)
Reproject: why important48
http%3A%2F%2Fwww.library.yale.edu%2FMapColl%2Ffiles%2Fdocs%2FUsing_Raster_Data.doc
Vocabulary49
Abbreviation Full
CRS Coordinate Reference System
SRS Spatial reference system (the same as CRS)
CS Coordinate system (CS != CRS or SRS)
Datum Spheroid axes and its relative position to the Earth
WKT Well-Known Text
EPSG European Petroleum Survey Group
OGC Open Geospatial Consortium
WGS84 World Geodetic System (1984)
GIS Geographic Information System
GML Geography Markup Language
UTM Universal Transverse Mercator
Main readings50
Google for it
Other readings53
QGIS tutorialhttp://www.qgistutorials.com/ru/docs/working_with_projections.html
Otherhttp://www.geo.hunter.cuny.edu/~jochen/GTECH201/Lectures/Lec6concepts/Map%20coordinate%20systems/UTM%20and%20UPS.htm
http://geology.isu.edu/wapi/geostac/Field_Exercise/topomaps/utm.htm
https://www.maptools.com/tutorials/grid_zone_details
https://en.wikipedia.org/wiki/List_of_map_projections
Practical lesson 0254
Resources:
Data:EPSG, http://www.epsg.org/ (needs registration)
Tools:To view EPSG:PostgreSQL, http://www.postgresql.org/ (open EPSG) + PgAdmin IIIor MS Access or MySQL
Practical lesson 0255
GeoTools Maven quick start:GeoTIFF plugin:CRS info: EPSG plugin for GeoTools (be sure to have):
http://docs.geotools.org/latest/userguide/tutorial/quickstart/maven.htmlhttp://docs.geotools.org/stable/userguide/library/coverage/geotiff.htmlhttp://docs.geotools.org/stable/userguide/library/referencing/crs.htmlhttp://docs.geotools.org/latest/userguide/library/referencing/hsql.html
Use Landsat 8 GeoTIFF for Moscow from previous lesson
Practical lesson 0256
1. Use Java to print out CRS of GeoTIFF and specified one 2. Use GDAL (gdalinfo, gdalwarp) to reproject rasters3. Use QGIS to visualize data in different projections
Data: Landsat 8 scenes
Next training (#3): a short quiz on coordinates and projections
Practical lesson 02: checklist57
1. Install OpenLayers Plugin2. Import vector/raster data in QGIS3. UTM Zone shapefile4. Project properties/CRS dialog box5. Pay attention to coordinates (false easting/northing)6. Identify features tool7. gdalinfo output8. try gdalwarp reprojection
