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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 surface Spheroid 1 Spheroid 2
Putting all together 5
Notes on CRS definition 6
select distinct coord_ref_sys_kind from 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 meters utm_c = cbind(470115, 6322515) utm_sp = SpatialPoints(utm_c, proj4string=CRS("+init=epsg:32637")) utm_sp # convert to (lon, lat) in WGS84 – units are degress global_sp <- spTransform(utm_sp, CRS("+init=epsg:4326")) global_sp
Ellipsoids 8
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Datum 9
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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 system 11
° °
° °
Can you port that on Java from C++? http://www.codeproject.com/Articles/15659/Longitude-Latitude-String-Parser-and-Formatter
Cartesian coordinate system 12
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
Projections 14
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http%3A%2F%2Fwww.nps.gov%2Fgis%2Fgps%2F04_datums_coordinatesystems_65.ppt
Why a map projection matters? 15
𝑑 = 𝑥1 − 𝑥22 + 𝑦1 − 𝑦2
2
Equirectangular projection 17
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•Link 1
The plate carrée (French, for flat square), is the special case where φ1 is zero.
UTM: Universal Transverse Mercator 18
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http://www.geo.hunter.cuny.edu/~jochen/GTECH201/Lectures/Lec6concepts/Map%20coordinate%20systems/UTM%20and%20UPS.htm
UTM: Universal Transverse Mercator 19
Apply a custom Transverse Mercator projection to each strip (zone)
Pic 1 Pic2 Pic3
UTM: Universal Transverse Mercator 20
• 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: zones 21
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• International Date Line) •
UTM: zones (another picture) 22
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• International Date Line) •
PIC
UTM: N & S 23
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 = 𝟒 𝟎𝟎𝟎 𝟎𝟎𝟎 𝒙 = −𝟐𝟎𝟎 𝟎𝟎𝟎 without false easting
UTM: distortion 25
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UTM: best practices 26
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Link 1
UTM: a limitation 27
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Universal Polar Stereographic system 28
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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 Grid 31
MGRS
Sinusoidal projection: very large scenes 32
Sinusoidal projection 33
http://modis-atmos.gsfc.nasa.gov/MOD04_L2/grids.html https://en.wikipedia.org/wiki/Sinusoidal_projection
EPSG database: www.epsg.org 34
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 != CRS 678 datum 14 variants of prime meridians 4232 CRS transformations (directly from to) 1829 revisions …..
21 tables
CRS Text Formats 35
Try GeoTools, GDAL http://docs.geotools.org/stable/userguide/library/referencing/crs.html http://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 interpretation 37
One of the EPSG goals is to give short codes for frequent combinations to exchange metadata, below WKT could be replaced by EPSG:32637
<geographic cs> <projected cs> UTM 37 North
<prime meridian>
EPSG codes interpretation (2) 38
PROJ.4 39
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 WGS84 40
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_ellipsoid https://en.wikipedia.org/wiki/Reference_ellipsoid
Reproject (raster=R, targetCRS=CRS, options) 43
Reprojection: the process 44
http://demo.geo-solutions.it/share/OptimizingRasterReprojection.pdf
Reproject: visualization in web maps 45
Reproject use case: scenes from different projections 46
Reproject: mosaic spanning several UTM zones 47
http://www.nrcan.gc.ca/earth-sciences/land-surface-vegetation/land-cover/north-american-landcover/9152 https://en.wikipedia.org/wiki/Canadian_Arctic_Archipelago
Lambert Conformal Conic (LCC) Ellipsoid Model: WGS84
(original Landsat projection is UTM)
Reproject: why important 48
http%3A%2F%2Fwww.library.yale.edu%2FMapColl%2Ffiles%2Fdocs%2FUsing_Raster_Data.doc
Vocabulary 49
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 readings 50
Google for it
Additional readings 52
Other readings 53
QGIS tutorial http://www.qgistutorials.com/ru/docs/working_with_projections.html Other http://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 02 54
Resources: Data: EPSG, http://www.epsg.org/ (needs registration) Tools: To view EPSG: PostgreSQL, http://www.postgresql.org/ (open EPSG) + PgAdmin III or MS Access or MySQL
Practical lesson 02 55
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.html http://docs.geotools.org/stable/userguide/library/coverage/geotiff.html http://docs.geotools.org/stable/userguide/library/referencing/crs.html http://docs.geotools.org/latest/userguide/library/referencing/hsql.html Use Landsat 8 GeoTIFF for Moscow from previous lesson
Practical lesson 02 56
1. Use Java to print out CRS of GeoTIFF and specified one 2. Use GDAL (gdalinfo, gdalwarp) to reproject rasters 3. 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: checklist 57
1. Install OpenLayers Plugin 2. Import vector/raster data in QGIS 3. UTM Zone shapefile 4. Project properties/CRS dialog box 5. Pay attention to coordinates (false easting/northing) 6. Identify features tool 7. gdalinfo output 8. try gdalwarp reprojection