Trace vector contours from a scanned map - Revision history

Neteler at 00:35, 7 December 2011

2011-12-07T00:35:35Z

← Older revision		Revision as of 00:35, 7 December 2011
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	[[Category:Documentation]]		[[Category:Documentation]]
	[[Category:FAQ]]		[[Category:FAQ]]
			[[Category:Vector]]

⚠️HamishBowman: /* View */

2010-02-27T17:18:03Z

View

← Older revision		Revision as of 17:18, 27 February 2010
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	* View shapefile in [http://qgis.org QuantumGIS]		* View shapefile in [http://qgis.org QuantumGIS]
	qgis chart_lines_gt5km/chart_lines_5km_crop.shp		qgis chart_lines_gt5km/chart_lines_5km_crop.shp


			== Convert to DEM ==

			* See the [[Contour lines to DEM]] wiki page.

⚠️HamishBowman: /* Preprocessing */ typo

2008-08-31T04:27:00Z

Preprocessing: typo

← Older revision		Revision as of 04:27, 31 August 2008
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	: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import. ''(see below)''		: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import. ''(see below)''
	: The Magic Wand select tool may be of great help here as well.		: The Magic Wand select tool may be of great help here as well.
	: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new ~~impage~~ with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.		: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new image with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.

	=== Import into GIS ===		=== Import into GIS ===

⚠️HamishBowman: /* Other ideas */

2008-08-31T04:22:00Z

Other ideas

← Older revision		Revision as of 04:22, 31 August 2008
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	== Other ideas ==		== Other ideas ==

	* Autotrace		* [http://autotrace.sourceforge.net/ Autotrace]
	* [http://potrace.sourceforge.net/ Potrace] [http://wiki.inkscape.org/wiki/index.php/Potrace from within Inkscape]		* [http://potrace.sourceforge.net/ Potrace] [http://wiki.inkscape.org/wiki/index.php/Potrace from within Inkscape]
	* [http://delineate.sourceforge.net/download.html Delineate]		* [http://delineate.sourceforge.net/download.html Delineate]

⚠️HamishBowman: links

2008-08-31T04:21:05Z

links

← Older revision		Revision as of 04:21, 31 August 2008
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	''Done!''		''Done!''

			== Other ideas ==

			* Autotrace
			* [http://potrace.sourceforge.net/ Potrace] [http://wiki.inkscape.org/wiki/index.php/Potrace from within Inkscape]
			* [http://delineate.sourceforge.net/download.html Delineate]
			* Newer versions of [http://www.inkscape.org Inkscape] can be used to extract vector features from a PDF into a format that can be loaded into the GIS, such as DXF (pehaps with a SVG->DXF tool)


	[[Category:Documentation]]		[[Category:Documentation]]
	[[Category:FAQ]]		[[Category:FAQ]]

⚠️HamishBowman: /* Import */

2008-08-31T04:15:21Z

Import

← Older revision		Revision as of 04:15, 31 August 2008
Line 3:		Line 3:
	'''Import a scanned map image'''		'''Import a scanned map image'''

			=== Preprocessing ===
	* To save processing later you might want to mask out obvious text and other noise in a paint program first.		* To save processing later you might want to mask out obvious text and other noise in a paint program first.
	: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import. ''(see below)''		: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import. ''(see below)''
	: The Magic Wand select tool may be of great help here as well.		: The Magic Wand select tool may be of great help here as well.
	: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new impage with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.		: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new impage with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.

			=== Import into GIS ===

	* Import image into GRASS (probably into a simple XY location)		* Import image into GRASS (probably into a simple XY location)
	r.in.gdal		r.in.gdal
	~~g.region rast=input_image~~

	* [[Georeferencing \| Georectify]] map using GUI georectifier or i.points + i.rectify		* [[Georeferencing \| Georectify]] map using GUI georectifier or i.points + i.rectify

⚠️HamishBowman: /* Prepare raster for conversion */

2008-08-31T04:13:35Z

Prepare raster for conversion

← Older revision		Revision as of 04:13, 31 August 2008
Line 48:		Line 48:
	* Sometimes it helps to "grow" the contours before thinning, especially when the scan is not of high quality and contours have "breaks" in them. Note that you may have to repeatedly try different radius values to get the desired effect.		* Sometimes it helps to "grow" the contours before thinning, especially when the scan is not of high quality and contours have "breaks" in them. Note that you may have to repeatedly try different radius values to get the desired effect.
	r.grow in=chart out=chart_grown radius=n_cells		r.grow in=chart out=chart_grown radius=n_cells

			=== Run the conversion ===

	* Convert raster lines to vector lines		* Convert raster lines to vector lines

⚠️HamishBowman: /* Import */

2008-08-31T04:12:56Z

Import

← Older revision		Revision as of 04:12, 31 August 2008
Line 4:		Line 4:

	* To save processing later you might want to mask out obvious text and other noise in a paint program first.		* To save processing later you might want to mask out obvious text and other noise in a paint program first.
	: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import.		: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import. ''(see below)''
	: The Magic Wand select tool may be of great help here as well.		: The Magic Wand select tool may be of great help here as well.
	: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new impage with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.		: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new impage with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.

⚠️HamishBowman: /* Convert to vector map */

2008-08-31T04:12:05Z

Convert to vector map

← Older revision		Revision as of 04:12, 31 August 2008
Line 17:		Line 17:

	== Convert to vector map ==		== Convert to vector map ==

			=== Isolate contour lines ===
			''(see also pre-processing hints above)''

	* Check how many categories (map colors)		* Check how many categories (map colors)
Line 37:		Line 40:
	1 = 1 black		1 = 1 black
	EOF		EOF

			=== Prepare raster for conversion ===

	* Thin the lines to be 1 raster cell wide		* Thin the lines to be 1 raster cell wide

⚠️HamishBowman: /* Import */

2008-08-31T04:10:26Z

Import

← Older revision		Revision as of 04:10, 31 August 2008
Line 6:		Line 6:
	: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import.		: For example, load the image into [http://www.gimp.org the GIMP] and cut away boxes of text, etc. If you are interested in a specific feature (such as solid black contour lines) you might try to isolate those by "Select -> By color" to pick out everything black, then "Select -> Invert" to pick everything that isn't black, and then "Edit -> Cut" to remove those parts of the image that we are not interested in. It helps if the original image starts with an indexed color palette. You also have the option of using GRASS's r.mapcalc module and other raster analysis modules to simplify the image after import.
	: The Magic Wand select tool may be of great help here as well.		: The Magic Wand select tool may be of great help here as well.
	: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new impage with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.		: If the orignal file was a GeoTIFF, the paint program will typically strip off any geocoding metadata upon re-save. You can read those off with ''gdalinfo'' and reapply with ''gdal_translate'', or use the original image+''gdal_translate'' to create a TFW world file which can be used on the new image. Another option is to dump the metadata to a file with the ''listgeo'' program and reapply to the new impage with the ''geotifcp'' program. Both these come with the [http://download.osgeo.org/geotiff/libgeotiff/ libgeotiff] software distribution. If using these tools it is important not to alter the dimensions of the image. See the [http://www.remotesensing.org/geotiff/faq.html#preserve_metadata GeoTIFF FAQ] for more information.

	* Import image into GRASS (probably into a simple XY location)		* Import image into GRASS (probably into a simple XY location)