The study and mapping of land surfaces, including relief (relative positions and elevations) and the position of natural and constructed features.

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9
votes
3answers
681 views

What are common methods for converting raster digital elevation data to vector contours?

In researching this I have found many references to the opposite, creating elevation data from contours, but nothing regarding contour creation. Preferably, I am looking for open source solutions like ...
8
votes
4answers
2k views

How to aquire a topographical map of Britain?

First of all, let me say that I know next to nothing about GISs. I'm trying to find / make / aquire a topographical map of britain. I want to use it as a height map in Dwarf Fortress so it needs to ...
7
votes
3answers
241 views

What does this style of line on Topographic maps indicate

If I was reading the purpose of this stackexchange site right, I could also ask general map questions. Not necessarily regarding software. Anyways, I was wondering if someone could inform me what ...
6
votes
1answer
2k views

Calculate Topographic wetness index in SAGA

i am currently working on a project which involves the quantification of the wetness in certain areas. However it produces quite different results from what i expected. I'll describe the steps i have ...
5
votes
2answers
169 views

What's the difference between hypsography and topography?

I've recently come across some data that has been labeled "hypsography". I looked it up and it sounds like topography. But this data source has data labeled "topography" separate from its ...
4
votes
2answers
198 views

how do you identify ridges on an elevation raster?

I was wondering whether anyone might be able to tell me in layman's terms how to extract or differentiate between ridges and hilltops from 10m elevation data using ArcGIS 10.1? Any advice would be ...
4
votes
1answer
676 views

Terraserver replacment - source for US Topo maps?

Now that Terraserver has been shut down (or at least that's how it appears), is there an alternative WMS server for US topo maps? Probably too much to hope to find one that provides vector layers ...
4
votes
1answer
302 views

How to restrict or block certain paths in NetworkX graphs?

I am trying to calculate shortest path between 2 points using Dijkstra and A Star algorithms (in a directed NetworkX graph). At the moment it works fine and I can see the calculated path but I would ...
4
votes
1answer
438 views

USGS Topographic Map Online API

I am creating a website for a non-profit organization and would like to plot points on a map similar to this: http://www.arcgis.com/home/item.html?id=931d892ac7a843d7ba29d085e0433465 I am currently ...
4
votes
3answers
604 views

Australian Topo Map GeoTIFFs

Does anyone know if Australian topo map GeoTIFFs are made available anywhere (preferably for free)? LINZ makes them available in New Zealand - http://www.linz.govt.nz/topography/topo-maps/index.aspx ...
3
votes
4answers
2k views

Add UTM labels to grid in qgis

I try to use qgis to create a custom topographic map for outdoor use: UTM, 1:50000. What these maps usually have is a 1km x 1km grid, which at the bottom is labeled with a shorthand for the ...
3
votes
2answers
88 views

Why are poles missing from GIS topographic data?

Why are poles data missing from most topographic resources ? Data from 60⁰ to 90⁰ lat frequently missing from topographic GIS data. Example with SRTM4.1: Common sense or deduction lead me to think ...
3
votes
1answer
253 views

Mapping points from total station data in Angle, Horizontal Distance, Vertical Distance

I am working on creating a contour map from total station topo points in ArcGIS 10. The points were collected using H angle, HD, VD instead of XYZ points. I need to create points from these ...
3
votes
1answer
72 views

What function should I use to assess the degree of elevational change (rocky cliffs etc.) of a DEM?

I have a DEM of my research area and I want to assess how the topography/elevation changes. I am specifically looking to see what areas may be good suitable bat-roosting habitat so I am trying to ...
3
votes
1answer
725 views

Map Grid Index / Reference for Canadian Topo Map

Does anyone know where I can find some kml at different resolutions to show the grid reference for the Canadian topographic maps (CanTopo and toporama). Much like is displayed on the map here: ...
3
votes
0answers
104 views

How to compute surface of raster or any point using ARCGIS?

I have a raster image whose values are a digital elevation model of terrain. I need to know the surface type (topographic characterization) of particular points along transects of this DEM. How to ...
3
votes
0answers
30 views

Library for parsing scientific PDS files?

Does a library exist for parsing the PDS files that scientific planetary data gets shipped as? For example, here's a link to to the lunar topographic data from the Lunar Reconnaisance spacecraft ...
2
votes
2answers
67 views

Gdal: highest and lowest point/pixel, how to get their altitudes?

Given a .tiff topographic raster image. How to get the altitudes of the highest and lowest point/pixel ?
2
votes
1answer
385 views

Polygonize.py outputs into a single file or simple merge?

Given an unique raster topographic file at start, I want to get vector polygons for elevations thresholds 1m, 200m, 500m, 1000m, 2000m into a single shp file. I first slice my raster into 5 (or more) ...
2
votes
1answer
142 views

I want to create my own topographic map

I need to create topographic maps for scales between 1:100,000 and 1:500,000. This is due to the fact that the official topographic maps in my country are offered in 5k, 10k, 25k, 50k, 100k and 500k. ...
2
votes
1answer
248 views

European Mountains Shapefile Data Sources

I am trying to locate a GIS freely downloadable shapefile (preferably polygon) of European main mountain chains (not an elevation data), eg Alps, Carpathian Mountains. I tried variuos sources , ...
2
votes
2answers
297 views

A library/software to create DEM from a topographic map

In one of my projects I need to digitize video clips showing some natural landscape. Specifically I need to know distances between different areas and elevation levels. I have a topographic map of ...
2
votes
1answer
76 views

How to create a buffer on a linestring with varying or increasing/decreasing width

I want to buffer rivers/streams for a topographic map. I'm using a PostgreSQL/PostGIS database. Usually, I create buffer with ST_Buffer with a constant width. For example, the width of a river buffer ...
2
votes
1answer
42 views

Calculating Topographic Exposure with Raster Calculator

I need you help trying to calculate Topographic Exposure (TOPEX) on a DEM in ArcGIS. I am trying to figure out wind exposure on a DEM with 25m cells. There is a great blog post where someone explains ...
2
votes
0answers
179 views

How to limit a specific area in order to have a topographic 3D map using MatLab?

I am using MatLab, I want to build a topographic 3D map, I am following this guide, I have been doing the steps listed on the section Draping Geoid Heights over Topography, and I do not have any ...
1
vote
3answers
104 views

Topography: How to get the x,y,z coordinates of highest or lowest point/pixel of a raster GIS?

Given a .tiff topographic raster image with mountains and deep sea, I am looking for the x,y,z specifics of the highest or lowest point. The x,y,z values being: altitude (z-coordinate) latitude ...
1
vote
1answer
32 views

Rough edges on tiles in QGIS

I'm loading four .ASC files into QGIS, each containing topographical data about a tile of 10 x 10 km. On the map, this data is displayed as black/white and different shades of gray. My problem is that ...
1
vote
1answer
1k views

Can Compound Topographic Index (CTI) / Topographic Wetness Index (TWI) produce negative values?

I am calculating Topographic Wetness Index for a study area using SRTM DEM (90 and 30m). I've seen several versions of TWI (CTI). I have been using: TWI = ln(As +1 / tanB) where As = ...
1
vote
2answers
127 views

Where can I programmatically download SRTM_V4.1 data?

SRTM v4 is an effort by the folks at CIAT-CSI to scrub, polish, and remove gaps in the raw SRTM data released by NASA (SRTM 3). One userfriendly interface : http://dwtkns.com/srtm/ provides ...
1
vote
1answer
315 views

ArcGIS Online Topo Maps

ArcView 10.1 does not have this kind of topo map to "Add Data". Where do I find this type of topo map, preferably free. ArcGIS online does not seem to offer this type of topo, unless I am not seeing ...
1
vote
2answers
97 views

viewshed analysis for observers wearing visors?

I'm starting with a DEM, and looking to identify every point that can be directly "seen" from any point in a particular polygon on an overlaid layer defining an area on that DEM - like any other ...
1
vote
1answer
357 views

What are Bands, Dimensions, and Histograms in QGIS?

First; I can see a band as synonymous with a channel in an image editing program like GIMP, is this correct? If so then bands play the role of color mixing and masking. Are there any other ...
1
vote
0answers
27 views

What steps does SAGA GIS take when calculating Topographic Wetness, specifically when handling depression filled (by ArcMap) DEM

I am a grad student involved with hydrological modeling. In the model I work on, we are calculating the Topographic Index (TI; without transmissivity - or set to 1) using Quinn's MFD algorithm. We do ...
1
vote
0answers
238 views

Topography: How to convert raster into vector layers?

(nb:This project is part of the #Wikipedia #wikimaps project) 1. Question: How to create vector topographic maps from raster image ? How to convert raster topographic image into closed vector ...
1
vote
0answers
112 views

cut/fill calculation tool to investigate if there is enough material to achieve a 30 degree slope

This is a cut/fill problem. We have pits that have been dug in the ground, usually rectangular. They have a bund wall around them. They are being rehabilitated by pushing the bund back into the pit. ...
0
votes
1answer
177 views

How to conditionnally assign a new value to pixels of a raster image?

Given a topographic GIS raster of one country crop.tif: Given a know pixel value such as elevation (z) is +73 : $ gdallocationinfo crop.tif 1 1 -valonly > 73 Given an elevation threshold n = 50 ...
0
votes
2answers
150 views

Gdal: How iterate through all pixels of a raster image?

Given a topographic raster image. How to iterate through all pixels of this raster image ? Solution preferably with gdal, in console. Some other libraries/script could be installed. Related: ...
0
votes
1answer
124 views

Gdal: How to get a pixel's value from raster image?

Given a topographic raster image. Given a pixel's coordinate in pixel/lines or geocoordinate. How to get it's pixel value ?
0
votes
1answer
207 views

Plotting Smith and Sandwell global seafloor topography grids

Does anybody have any experience with plotting Smith & Sandwell 2-minute Mercator-projected grids in ArcGIS? I've downloaded one in two formats: ers and img. I've found tools for processing .img ...
0
votes
1answer
85 views

Gdal_polygonize: How to filter pixels above a given value (elevation)?

Given a topographic GIS raster of one country: Given an elevation threshold n = 50 (meters) How to polygonize pixels when z >= n ? gdal_polygonize.py is not clear on this point. It states This ...
0
votes
0answers
108 views

How to calculate Gradient from DEM?

I have a digital elevation model for a catchment area and I would like to calculate the gradient by cells. Is that possible and does anybody know the steps?
0
votes
0answers
114 views

How can I calculate raster cell area for upslope contributing area

I am new to spatial analysis, and urgently trying to follow this tutorial to generate a topographic wetness index for my area of interest: ...