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Geoapplications development  · UTM: False Easting and False Northing 24 Link 1 False easting False...

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Geoapplications development http://rgeo.wikience.org Higher School of Economics, Moscow, www.cs.hse.ru
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Page 1: Geoapplications development  · UTM: False Easting and False Northing 24 Link 1 False easting False northing North zones 500,000 m none South zones 500,000 m 10,000,000 m Link 2 False

Geoapplications development

http://rgeo.wikience.org

Higher School of Economics, Moscow, www.cs.hse.ru

Page 2: Geoapplications development  · UTM: False Easting and False Northing 24 Link 1 False easting False northing North zones 500,000 m none South zones 500,000 m 10,000,000 m Link 2 False

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

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Map projection (leads to distortions) 3

https://en.wikipedia.org/wiki/Geoid

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Datum: aligning spheroid (ellipsoid) 4

Geoid/Earth surface Spheroid 1 Spheroid 2

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Putting all together 5

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Notes on CRS definition 6

select distinct coord_ref_sys_kind from epsg_coordinatereferencesystem

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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

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Ellipsoids 8

Page 9: Geoapplications development  · UTM: False Easting and False Northing 24 Link 1 False easting False northing North zones 500,000 m none South zones 500,000 m 10,000,000 m Link 2 False

Datum 9

https://en.wikipedia.org/wiki/Geodetic_datum

https://en.wikipedia.org/wiki/World_Geodetic_System

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Coordinate systems (CS) 10

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Cartesian coordinate system 12

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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

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Projections 14

http%3A%2F%2Fwww.nps.gov%2Fgis%2Fgps%2F04_datums_coordinatesystems_65.ppt

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Equirectangular projection 16

Link 1

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Equirectangular projection 17

•Link 1

The plate carrée (French, for flat square), is the special case where φ1 is zero.

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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

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UTM: zones 21

• International Date Line) •

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UTM: zones (another picture) 22

• International Date Line) •

PIC

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UTM: N & S 23

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UTM: False Easting and False Northing

24

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

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UTM: best practices 26

Link 1

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UTM: a limitation 27

• ° °

Link 1

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Universal Polar Stereographic system 28

Link 1

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Military Grid Reference System (MGRS) 29

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Military Grid Reference System (MGRS) 30

o

o

o

Link 1

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NASA WW Example: MGRS Grid 31

MGRS

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Sinusoidal projection: very large scenes 32

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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

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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/

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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

36

http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html

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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>

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EPSG codes interpretation (2) 38

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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

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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

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Ellipse (1) – ellipsoid (2) – spheroid (3) – oblate spheroid, ellipsoid of revolution, reference ellipsoid, Earth ellipsoid (4)

41

Wikipedia: Ellipse Wikipedia: Spheroid

Wikipedia: Ellipsoid

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Ellipse (1) – ellipsoid (2) – spheroid (3) – oblate spheroid, ellipsoid of revolution, reference ellipsoid, Earth ellipsoid (4)

42

(2) (3)(4)

SPHEROID["WGS 84", 6378137, 298.257223563,

AUTHORITY["EPSG","7030"]]

)

https://en.wikipedia.org/wiki/Earth_ellipsoid https://en.wikipedia.org/wiki/Reference_ellipsoid

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Reproject (raster=R, targetCRS=CRS, options) 43

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Reproject: visualization in web maps 45

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Reproject use case: scenes from different projections 46

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Reproject: why important 48

http%3A%2F%2Fwww.library.yale.edu%2FMapColl%2Ffiles%2Fdocs%2FUsing_Raster_Data.doc

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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

Page 50: Geoapplications development  · UTM: False Easting and False Northing 24 Link 1 False easting False northing North zones 500,000 m none South zones 500,000 m 10,000,000 m Link 2 False

Main readings 50

Google for it

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Main readings 51

http://grassbook.org/

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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

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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

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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

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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

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