Questions tagged [elevation]

The vertical distance of a point or object above or below a reference surface or datum (generally mean sea level).

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19
votes
4answers
40k views

Extracting elevation from .HGT file?

I want to assign a specific long/lat position on a map to the elevation from SRTM3 data files, but have no idea how to find the specific value. So I want some example of how I can find in N50E14.hgt ...
15
votes
4answers
5k views

Elevation profile 10 km each side of a line

How can I get an elevation profile for a band of terrain? The highest elevation within 10 km (on each side of the defined line) should be taken into account. I hope my question is clear. Thank you ...
10
votes
3answers
21k views

How to create contour lines from point data using QGIS?

I'm using QGIS 2.4.0 and I have a shapefile of points with elevation data and X and Y coordinates. I'm using windows 7 OS. The idea is to create a contour line SHP using my point data. My question ...
2
votes
1answer
7k 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 (...
15
votes
5answers
26k views

Seeking free elevation data for Europe?

Where can I find free elevation data for Europe? The available resolutions and terms of use are important details that I also seek.
16
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4answers
8k views

Calculating elevation profile along line from a DEM?

Given a DEM (Digital Elevation Model) and a line (x1,y1) --> (x2,y2) (paired coordinates (x,y)), how can one calculate the elevation profile or cross-section projected on that line? I am looking for ...
10
votes
1answer
6k views

Python Script for getting elevation difference between two points

I have several stream segments 1000 Km long. I need to find the elevation difference between two consecutive points of distance 1 Km starting from the upstream to downstream. How can I get the ...
11
votes
1answer
44k views

Calculating elevation profile for a polyline in ArcGIS 10?

My elevation data is a floating point tif. I have a road for which I need to calculate the elevation profile, but I can't see the tools to do this. Can I do this with ArcGIS, with spatial analyst/3D ...
6
votes
2answers
7k views

Exporting DEM-derived rasters to CSV from QGIS?

I have been able to import into QGIS a set of raster topographic maps and the associated DEM raster maps. It registered the two for me. From there I have calculated the associated slope raster map. ...
48
votes
7answers
50k views

Choosing colour-ramp to use for elevation?

This is maybe rather subjective as it concerns style, but I would like to have a few decent colour ramps for my DEM when it is layed over my hill-shading. I have created the Swiss hillshade model as ...
22
votes
6answers
11k views

How to download the entire ASTER GDEMv2 dataset?

In October 2011, NASA released the new ASTER GDEM global dataset (30m) and I have been wanting to get my hands on it. The only problem is that it takes forever to download and I do not feel like ...
7
votes
1answer
2k views

Programmatically download (seamless) NED tiles?

I used to download 1/3 arcsecond elevation geotiffs from extract.cr.usgs.gov using web services. But a few days ago, that stopped working, probably because USGS reorganized their site. I tried ...
6
votes
1answer
5k views

What is the highest obtainable resolution of FREE elevation data in the UK?

I am seeking closure with this question guys. I am aware of various sources of free elevation data ~30+ m, and I have been searching for higher resolution FREE data for a while now. This already ...
2
votes
2answers
196 views

Increasing Flood Plain

I am doing a project where we are attempting to determine how many more buildings would flood if the FEMA flood plain increased by 1',2' and 5'. I have the elev of the flood plain rasters from lidar ...
15
votes
5answers
19k views

Calculating Topographic Ruggedness Index in ArcGIS Desktop?

Does anyone know how to calculate Topographic Ruggedness Index in ArcGIS Desktop without access to command line ArcInfo Workstation? "The topographic ruggedness index (TRI) is a measurement developed ...
1
vote
1answer
2k views

QGIS elevation and relief shade

I am trying to generate a map with terrain and elevation in QGIS and as a beginner I have followed tutorials on how to generate contours and hill shades succesfully. However, I don't know what are the ...
15
votes
5answers
12k views

How to get an elevation profile for a gps track?

I'd like to get a reasonably accurate elevation profile for a track recorded with a GPS (which often has very unreliable altitude data and occasionally none at all, depending on the model.) Does ...
10
votes
4answers
9k views

Getting elevation at lat/long from raster using python?

I was wondering if anyone has some experience in getting elevation data from a raster without using ArcGIS, but rather get the information as a python list or dict? I get my XY data as a list of ...
2
votes
2answers
3k views

Modifying DEM elevation data in QGIS using a polygon

I've tried searching through the existing questions but am struggling to find a succinct answer to what I am trying to achieve. For background, I am running a flood model in TUFLOW to help support a ...
9
votes
6answers
2k views

seeking “Available Sky” implementations

I'm looking for implementations of an algorithm called "Available Sky". ArcGIS (Spatial Analyst or GRID) is preferred, but solutions in GDAL, SAGA GIS or others are perfectly acceptable. The ...
7
votes
1answer
2k views

What resampling technique should be used to reproject an altitude raster?

Does anyone know whether I should choose: nearest, bilinear, cubic or majority when projecting the WorldClim altitude raster layer?
5
votes
5answers
2k views

Google Earth Polygon surface area to follow the curvature of the earth model

Question: When drawing a polygon in Google Earth with latitude, longitude and elevation values at each node, how do you ensure that the surface area of the polygon also represents the desired ...
4
votes
2answers
872 views

Kriging values greater than the most extreme value of the input layer?

I'll admit I don't understand kriging to the fullest. Yet, I've read that the weights should add up to 1 as in IDW and Natural Neighbors. However, surrounding the biggest elevation points of my ...
4
votes
1answer
874 views

Converting elevations into correct units with pyproj?

I am converting a point from wgs84 into a state plane coord system (epsg: 32051, which is defined in US survey feet) using pyproj, but the transform isn't changing the z values into feet: point_4326 =...
3
votes
1answer
977 views

Performing viewshed analysis with Dutch AHN files in QGIS?

i downloaded the new (dutch hight data) AHN files, and was trying to perform a viewshed analysis at some point near UTRECHT. The plugin (grass plugin) works ok, i tried it before with a dem map. ...
2
votes
3answers
3k views

How to update the Z value using an UpdateCursor?

I have created the following script to mimic the ArcGIS 3D Analyst tool, FeatureTo3DByAttribute, which creates a 3D copy of a 2D feature class and sets the Z to a specified attribute. import arcpy, ...
1
vote
1answer
723 views

Replicate elevation profile extraction (3D Analyst toolbar) in ArcPy

How can I replicate in ArcPy the 3D Analyst Toolbar operations which extract an elevation profile from a transect line drawn atop an elevation layer? This will be incorporated into an automated ...
0
votes
0answers
87 views

Granularity of elevation in GMTED2010 data / understanding shapefiles

Following on from Records of shapefile do not contain every field, where @scruss provided some very helpful Python code. I seem to have a fundamental inability to understand a shapefile (reader ...
32
votes
6answers
5k views

How to interrupt contour lines beneath elevation labels (instead of using label buffers)?

Is there a way to interrupt a contour line beneath an elevation label?
8
votes
2answers
7k 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?
13
votes
2answers
2k views

What is the smallest contour interval possible when derived from a DTM?

I am converting a 2m DTM to contours, and would like to have the smallest interval possible. Is there a theoretical limit, or even a rule of thumb for defining contour intervals based on the ...
10
votes
1answer
1k views

Generating DEM from isolines and spot heights using GRASS?

I have two shape files containing height information of a certain area and I need to create a raster DEM with GRASS using them. file 1 consists of height information in contours (isolines) file 2 ...
5
votes
2answers
4k views

How to read GeoTIFF using PHP?

My current pet project involves creating a web service that uses the CGIAR SRTM worldwide elevation data set. Each request to the service will query for elevation data from a small geographic area. ...
14
votes
2answers
1k views

Why does GPS altitude jump sometimes?

I am currently developing a little application in Android which uses GPS. When i click a button i start to record a "track". If i walk around i save my position every second into a file. This works ...
10
votes
3answers
17k views

Reading National Elevation Dataset (ArcGrid/GridFloat/IMG) with Python only tools?

I've found high precision elevation (1/3 - 1/9 arcsecond resolution) data from the National Elevation Dataset provided by the USGS. It comes int IMG, Arcgrid, and GridFloat formats. I know ArcGrid ...
6
votes
1answer
7k views

Displaying elevation profile and storing DEM elevation back to KML line using QGIS?

When I draw a track in Google Earth, for example along a road, I can right-click it to "Show elevation profile", and it displays a 2D plot of distance vs elevation. However, if I save the KML, the ...
5
votes
1answer
636 views

Identifying south facing mountain land, above an elevation, within a slope range, less than fixed distance from major roadways

This odd question comes from believing that such an analysis is plausible in a GIS system. Only, I don't how to accomplish the various discrete steps implied from the Title, nor where to get a topo ...
4
votes
6answers
4k views

shadow simulation from buildings [duplicate]

is it possible to use hillshade function in ArcMap to calculate shadow areas of buildings or simulate shadows of buildings, using DSM of the buildings and the sun angle and azimuth?
3
votes
1answer
701 views

Why not measure elevation from the center of the earth?

In trying to understand Geoid vs Ellipsoid height, I ran across this page. One of the claims is: Zero elevation as defined by Spain is not the same zero elevation defined by Canada Basically, ...
2
votes
1answer
2k views

Querying Elevation Data in Postgis

Problem: I have a bunch of raster data (DTED) and I want to use this to make elevation queries using PostGIS (if it makes sense). E.g. I want to ask the question "what is the elevation at (lat1,lon1), ...
10
votes
2answers
1k views

Elevation profile sample point algorithm

In generating an elevation profile, samples from the underlying raster must be taken. If the objective is to create a profile of maximum quality, how should the locations of sample points be ...
9
votes
7answers
4k views

Is there an online tile-based elevation service?

I am working on an application that requires the elevation at a given lat/long coordinate for lots of closely spaced coordinates along any given irregular path. (The path is a trace of a glider/hang-...
5
votes
1answer
278 views

Creating a point corresponding to the maximum elevation of a DEM [duplicate]

I am wondering how can I create a point corresponding to the maximum elevation value of a DEM. I mean, from the DEM I can easily get the maximum elevation. For the sake of a viewshed analysis, I would ...
4
votes
1answer
3k views

How to obtain a DTM/DEM from DSM

I need to obtain a grid of bare ground elevation (removing all edifices, trees, roads and man-made elements) for quantitative geomorphological analysis from a high resolution (1 m) DSM obtained by ...
4
votes
2answers
364 views

How to form a V-Shape field of view from any given point (i.e. latitude longitude)

I want to visualize the V-Shape polygon which can be referred to field of view as well. So, far i have been able to find the latitude and longitude of a certain point when i give an input of latitude ...
2
votes
1answer
2k 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
1answer
555 views

How to calculate difference in elevation between a POINT and the surrounding cardinal directions?

I have a POINT shapefile (Rain gauges) and a 100m DTM in the same coordinate system. Is there a method using QGis to calculate the difference in elevation between the elevation of each rain gauge ...
14
votes
1answer
374 views

Creating Buffer Polygon following Elevations using ArcGIS Desktop?

What I'm looking to do is put a 100 m buffer on a polygon, but rather than the buffer being at a fixed width "as the crow flies" I want it to follow the slopes of my Lidar DEM. I have ArcMap (with 3D ...
7
votes
1answer
889 views

Which is better for measuring actual ground elevation, NED or SRTM?

I know that NED DEM layers are created using mainly Lidar point clouds and that the SRTM derives its data from shuttle-based radar. I have both of these loaded into QGIS and can see that over my study ...
7
votes
4answers
5k 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"...