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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3
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1answer
741 views

Recommendations for creating contour map from depth points

I am trying to put together a safe routes map for a local lake. I have an old paper map that has a grid of various depths as points. I would like to draw contour lines through these points and create ...
0
votes
0answers
19 views

Creating DEM using ArcGIS 10.1? [on hold]

I am trying to create a DEM. Is it true that creating said DEM is done by using the 3D Analyst tool, then applying raster interpolation and then the "Topo to raster" tool? Is that it? Or do I have to ...
7
votes
2answers
3k 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?
0
votes
0answers
7 views

Plot GPX on topographic map with no labels

I am trying to plot a path from a GPX file on a topographic map with as few labels as possible. I've played around with a handful of both online and desktop solutions, but it seems that I either don't ...
2
votes
0answers
37 views

Negative reflectance values after topographic corrections (cosine correction and modified Minnaert correction)

I am trying to manually correct the surface reflectance values of some Landsat 7 and 8 images. I'm using Minnaert modified method, which uses the cosine correction as one of its inputs (see below the ...
1
vote
1answer
72 views

Positive Topographic Openness - do any FOSS tools (other than SAGA) provide this?

I'm looking for a FOSS GIS tool to provide Positive Topographic Openness on 32-bit Ubuntu. (which rules out ArcGIS) Normally I use SAGA GIS for this, but my Ubuntu setup is a bit messed-up after a ...
1
vote
0answers
44 views

Error with SAGA's Topgraphic Correction

I am using QGIS 2.14.2, trying to perform a supervised classification on a rapideye image with the SCP plugin. To improve my classification im trying to work with the SAGA's topographic correction. I'...
10
votes
3answers
153 views

Calculating sunrise/sunset time while considering topography

I want to calculate the sunrise and sunset times for a full year for a given location taking topography into account. Perhaps sunrise/sunset are not the right terms, but what I want is the time at ...
4
votes
1answer
72 views

30m/10m/1m resolution DEM for microtopography research

I am conducting research in a region of Illinois that does not have a LiDAR dataset. I am looking to develop a fine scale habitat species distribution model; however, the coarse data available (30m/...
7
votes
3answers
568 views

Is there a difference between the Planchon & Darboux and Wang and Liu depression filling algorithms? Other than speed?

Can anyone tell me, based on actual analytical experience, if there is a difference between these two depression filling algorithms, other than the speed at which they process and fill depressions (...
3
votes
1answer
64 views

Topographic Position Index unexpected result in QGIS

I am using Windows 7 enterprise and QGIS version 2.12.2 Lyon. Have found an unexpected result when I use QGIS to generate a topographic position index (TPI) raster from a 30m by 30m DEM. I find a ...
1
vote
1answer
47 views

How to do diagram block with open source software?

I would like to do a block diagram (topographic and geological representation). Is it possible to do this with QGIS (or other open source software), in Windows 7?
0
votes
1answer
319 views

Plotting Smith and Sandwell global seafloor topography grids in ArcGIS Desktop?

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 ...
2
votes
2answers
38 views

How can I alter the value field in a raster?

I'm using ArcGIS. I have a raster with angles in the value field. But the value field is type long integer. I would like to change it to float. Is that possible? Some more details: I've started with a ...
2
votes
1answer
995 views

Getting Negative Topographic Wetness Index (TWI) values in SAGA GIS?

I am getting negative topographic index wetness values in SAGA GIS - anyone else every get this? Not all negative values, but the minimum of the TWI range is negative for some steep watersheds we are ...
0
votes
1answer
48 views

Removing every second row and column cells from a raster file

I have a SRTM 3 arc second topography model (.tif file). If I remove every second row and column of cells from the grid, can it be said that the model becomes a 6 arc second? Or does SRTM 3 arc ...
3
votes
1answer
37 views

Importing Historic Maps into ArcGIS

I am trying to import a historic USGS map illustrating an island in the Mississippi River from 1953. I would like to project the scanned map onto a basemap without georefrencing with control points ...
1
vote
0answers
55 views

How to create buffers having regard to topography with QGIS

I want to create buffers of 25 kilometers around points in a point-shapefile with QGIS. My problem is that I don't need an air-line distance of 25 km around the points, but a "real distance" having ...
2
votes
1answer
114 views

What would a simple hillshade algorithm be?

I'm curious how GIS systems actually generate a hill-shade from input data like a raster DEM layer. I'd like to implement my own in software (mostly for fun/learning) but I want to start with a ...
1
vote
1answer
50 views

Creating DEM from topography map in QGIS [duplicate]

For my geology diploma project I need to create DEM from topography map my professor gave me to use as a base map. The map is georeferenced. My idea was to draw lines over the izolines of the map, ...
0
votes
1answer
36 views

free/open source Western Australian Topographical data

does anyone know (or have :P) a free or open source Western Australian Topographical datasets? I have a project that involves terrain relief in Northam, ideally they want it at a scale of 1;25,000 but ...
1
vote
0answers
30 views

I have a .adf file and want to select an elevation range [closed]

I'm super new to GIS. I downloaded a USGS 30m resolution map of a bay, and now I want to specify all areas that are between 0m and -30m elevation. I need to find where a defined area contains 0 and -...
1
vote
0answers
64 views

Strategies and methods that Datums and Coordinate Systems use to account for movement of the earth's surface

Are there datums and coordinate systems that address the issue of shifting coordinates through time? If so, what are some of the strategies and methods that the datums and coordinate systems use to ...
6
votes
4answers
2k 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 "hypsography"...
2
votes
1answer
53 views

Understanding concept of ArcGIS for Flex?

I am a complete newbie to GIS. I am trying to download topographic data from a website that displays a map that can be zoomed in and out. The website is setup with: This application is using ...
5
votes
1answer
138 views

How to add a topographic map to a shapefile?

I wonder how it's possible to add this topographic information (elevation) to the map of Santa Cruz Island and all of the Galápagos Island that I have here. library(rgdal) library(rgeos) library(...
2
votes
1answer
51 views

Quebec GIS Data

I'm looking for basic political borders for the province of Quebec, as well as property parcel data and topography. Any suggestions for inexpensive/free data?
5
votes
1answer
945 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 ...
0
votes
0answers
452 views

How can I calculate raster cell area for upslope contributing area

I am new to spatial analysis, and trying to follow this tutorial to generate a topographic wetness index for my area of interest: http://gracilis.carleton.ca/CUOSGwiki/index.php/...
6
votes
1answer
4k 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 ...
1
vote
0answers
213 views

Interpolate vector layer and raster layer data into regular grid data using QGIS

I'm new to using GIS software. I obtained two different sets of data: Topography data (raster, .asc) Bathymetry data (shapefile, .shp, etc) I include topography data using Add Raster Layer and ...
0
votes
0answers
52 views

Terrain elevation in QGIS

How can I get started with creating a map with elevation just like this one: Basically I need a map that looks like the one above. Can someone tell me where can I get the data, and how do I process ...
3
votes
4answers
234 views

How can Identify highs on a DEM?

I have a DEM and I want to find each hill and create a polygon for its area, effectively the out closed contour that encloses the hill. I can do this visually but I'm about to work on a larger area so ...
2
votes
0answers
84 views

Error when using SAGA's “topographic correction” algorithm in QGIS

I'm trying to do topographic correction of Landsat images using SAGA's "topographic correction" algorithm from QGIS' processing toolbox. I was able to do it using Minnaert Correction with slope and ...
4
votes
5answers
5k 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 ...
6
votes
0answers
123 views

FLAG - fuzzy landscape analysis in GIS [closed]

I am trying to identify wetlands using different topographic indexes, e.g. TWI/CTI. And I would like to try out a method called FLAG (fuzzy landscape analysis in GIS), but I don't really understand ...
5
votes
1answer
145 views

Why does the peak of a mountain appear bright on Radar images

Why does the top of a mountain appear bright on a SAR (radar) image. I know that the peak of a mountain is subject to a layover effect, thus appearing closer on the radar image than the bottom part of ...
5
votes
3answers
218 views

Ways to determine winding topographic characteristics of a river

Are there any methods and/or technical guides on how to classify the degree of winding of river bodies? I have the following polygon layer of roughly 100,000 water bodies and would like to write an ...
4
votes
1answer
1k 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 ...
2
votes
0answers
117 views

How do you merge overlapping .asc files in QGIS with topography and bathymetry?

Firstly, apologies for any incorrect terminology - this is my first time trying to manipulate GIS data. I have two files. The first is higher resolution (SRTM) topography data for a region of islands ...
1
vote
2answers
120 views

Topographical Elevations for Central Africa and Cameroon

I am using QGIS and I have been faced with the problem of topographical maps. From searching online I could only find data for the United States. Google maps offers elevation contours, however I am ...
5
votes
4answers
979 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 ,...
1
vote
0answers
65 views

Calculating “sun time” on areas with high mountains? Topography available

I'm wondering how to proceed if you want to calculate how a location on land will get direct sunshine at a given time on a given date (compared being in the shadow of the mountains)? The area is very ...
1
vote
0answers
90 views

Why does the “local maxima” module in SAGA GIS put so many “maxima” points on lakes and plains?

SAGA GIS puts too many maxima points on plains and lakes. Why does it happen? Is there a way to avoid this? It's not really a big problem (the value is correct) except for the size of the SHP files in ...
0
votes
0answers
64 views

How to make a map showing the slopes of the terrain

I am not too familiar with techniques, and was looking for ways to make a slope map for a given area. It ended with finding this site and posting the question. We are in the process of zoning a new ...
3
votes
3answers
928 views

Gdal: how to get the max and min altitudes of my topographic raster?

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

Can we create topographical map of private land using GPS elevation data?

Is there a way to create a relatively precise topographical map of a private land using GPS elevation data? As the land is a little bit over 100,000 square meters, the available regional topographical ...
13
votes
5answers
11k views

How to calculate Topographic Ruggedness Index in ArcGIS Desktop?

Does anyone know how to calculate Topographic Ruggedness Index in ArcGIS without access to command line ArcInfo Workstation? "The topographic ruggedness index (TRI) is a measurement developed by ...
0
votes
1answer
140 views

How do I take a contour .shp file and create a separate layer for each elevation?

The end result is to have a .dxf file in which each different elevation resides in a different layer. If at all possible I would like to be able to do the organizing in tile mill, or through some ...
1
vote
1answer
55 views

raster topo map with gaps to DEM

I'm trying to create a DEM from this raster map: I managed to clean all the shapes and text. I tried to write a program which finds the curve pieces and connects them. But, I realized that it is ...