Hot answers tagged topography
10
If you are looking to convert DEMs to contour lines:
QGIS Plugin Contours
For converting scanned topo maps to vector contour lines, Arcscan is one of the easiest (and most sophisticated) programs out there. However, there are several opensource alternatives, including a promising GRASS approach:
Trace vector contours from a scanned map.
Additional ...
7
First, you need to calculate at least the slope. F.ex I have the following data:
Then put the correct data as variables to the module:
And at last you should get the result:
UPDATE
With Catchment Area as input
the results are:
4
Based on your use-case, I'm guessing you won't need extremely high resolution data (many users are looking for 90 meter or better data) and are more interested in the consistency and visual presentation aspects of the data than its precise accuracy at a cell level. A nice dataset for this kind of use is CleanTOPO2, a global nominally 1km resolution dataset ...
4
You need to download the Land-Form Panorama OpenData (OpenData=free) dataset from Ordnance Survey
Download is for Great Britain only (England, Scotland & Wales only)
530MB
https://www.ordnancesurvey.co.uk/opendatadownload/products.html
Pros:
FREE
This product is supplied both as a set of contours and spot heights (x,z,y) and as a gridded digital ...
3
I would say that you're on the right track, and both slope and ruggedness would be useful for you. I'm not sure what angle cliff faces bats prefer but I'm assuming you know this.
To perform a slope analyis, you will need either the Spatial Analyst Extension or the 3D Analyst Extension. You want to run the Slope Tool. Once you've performed the slope ...
3
It may not show up under the Basemap dialog, but Esri does host a US Topo map service. The service uses scale dependent rendering with 4 levels, a colorized shaded relief, 250k topographic, 100k topographic, and 24k topographic.
ArcGIS.com
http://www.arcgis.com/home/item.html?id=931d892ac7a843d7ba29d085e0433465 or
ArcGIS Server REST endpoint
...
3
Another open source option which can easily be scripted using shell scripts or python is to use GDAL_Contour to generate contours from a dem file. I grabbed some example DEM data and ran this command to generate 10 m contours, saved as a shapefile:
gdal_contour -b 1 -a elevation -snodata -9999 ns67ne.tif contour.shp -i 10
The switches are:
-b 1 selects ...
3
I think that GRASS module r.contour has more functinality than QGIS' one. For example, you can set maximum and minimum levels for extracting contours. Plus, it has parameter cut which makes the output more generalized.
3
If I read correctly, you are looking for a replacement for the WMS service of the USGS Quad Maps. From what I can find, there doesn't seem to be a direct replacement for that. I think the closest you are likely to find is using the Seamlesss Data Warehouse. This is the USGS data portal for all the orthoimagery that they supply as well as their National ...
3
The add_edge method of a Graph in NetworkX takes a weight as an attribute. This is a proxy for traversal restriction. If the weight specified is high, then traversal algorithms will avoid that route. For example:
import networkx as nx
G=nx.Graph()
G.add_edge('a','b',weight=0.6)
G.add_edge('b','c',weight=0.2)
G.add_edge('c','d',weight=999) # this one is ...
2
Those look like the grids for the National Topographic System in Canada.
They can be downloaded from Geogratis as the Vector Indexes of the National Topographic System of Canada.
There is a folder in there called kml_files full of .kmz files.
If you prefer, you can get them more easily by downloading them zipped (15mb) at all scales from the WMS in ...
2
Are you looking for a height map or a topo map? These are not exactly the same.
If you want a grayscale (or any other scale for that matter) height map of Britain, one of the ways you can get that is using Maperitive's generate-hypsometric command.
Here's a sample heightmap I've just made for the northern Scotland (black is zero elevation, white is 1500m ...
2
To start off, you have to choose a coordinate reference system. The one used by Openstreetmap (EPSG:3857 or 900913) does not have real meters as units, because the horizontal lengths (latidues) are all equally squeezed, while they are getting shorter towards the poles in reality.
So you have to look for the UTM zone of your part of the world, or another CRS ...
2
Please have a look at Using Viewshed and Observer Points for visibility analysis
In the lower part of the article you will see that there are several parameters that you can use. The parameter that you need are VERT1 & VERT2
To use these parameters in your ViewShed Analysis, your input point featureclass should have fields with these names. The ...
2
I don't think there is a way of doing what you want, or if there is I don't know how to do it. Just at the moment I'm making eight maps that need this form of grid labelling and I'm having to add each grid ordinate as a label. It's taking me hours.
It should be possible to exercise some control on where grid ordinate labels appear on the map, using a ...
1
BANDS
When working with e.g. scanned maps raster the three (four) bands are exactly the same as RGB(A) channels in e.g. GIMP. But that does not apply to other kinds of raster data.
For example, remote sensing data such as multispectral images acquired from satellites can contain (almost) any number of bands with each pixel value for a specific band ...
1
You should not be seeing negative values in the CTI. Since you did not provide a reproducible example I cannot speculate as to why you are getting incorrect results. The expected range is not limited 1-10. The range will be defined by flow accumulation which is influenced by the size of the basins that are accumulating flow. The index does not rely on washed ...
1
MapConnect has 1:250k data for download in many formats, including as ECW rasters which can be converted to GeoTiff with GDAL if needed. They also have a partial coverage of 1:50k topographic maps, but they cost money.
If you're interested in creating your own topographic maps, check out TopOSM, which aims to produce high-quality topographic maps from open ...
1
The ArcGIS Javascript API in and of itself is free. However, to add your own content you would need a license to ArcServer.
You could use arcgisonline.com to create a map similar to the link you provided and add a spreadsheet that contains the plot points you want. This is a free service, however, I think there is a limit on the amount of features you can ...
1
There have been recent advancements to grids in QGIS. Two are PyQGIS plugins, the other a C++ map canvas decoration. While I don't think any of them will truncate the labels like you wish, they are all open source and GPL licensed.
You could edit one of these to add your features of reducing label text redundancy and centering of the label. The authors of ...
1
The new labeling engine in QGIS offers the possibility to place each label at a specific X-Y location. You need to add two new columns to the attrib table, say label_x, label_y. THen in the "Data Defined Settings" in the Labeling window, choose those two columns for "X coordinate" and "Y coordinate" respectively. Now you should be able (with editing enabled ...
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