The ratio between distances on a map and distances in the world

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45
votes
12answers
84k views

What ratio scales do Google Maps zoom levels correspond to?

Can anyone provide me with a link (or some details) on the actual ratio to "zoom level" figures for Google Maps? e.g. Google Maps Level 13 = 1:20000
3
votes
2answers
5k views

Why does QGIS scalebar show a wrong scale?

I'm using QGIS 1.7.1 and have added a scalebar. The scalebar usually displays in degrees, unless I switch the map's projection to meters, in which case the units are display in cm. This is not ...
5
votes
2answers
868 views

Scale and Z factor have no effect on hillshade analysis in QGIS

I used an SRTM DEM to create a hillshade in QGIS 2.2.0. However, the resultant hillshade seems to be vertically exaggerated. Also, changing the settings for scale and z-factor does not have any effect ...
13
votes
3answers
4k views

Changing symbology at different scales in ArcMap?

I am using ArcMap 10 and I want to display my village parcel symbology differently at given scales. I have one idea to copy and paste same layer. But my question is that in a single layer, is it ...
8
votes
6answers
954 views

Maps zoomed around specific locations (magnifying glass effect)

How do I create a static map where the scale varies based on location? Example: to drive from a specific location X in Albuquerque to a specific location Y in Chicago, I want to "zoom" around X and ...
7
votes
1answer
2k views

How to automatically generate useful scales for data driven pages in ArcGIS desktop

I have been tasked with creating several hundred maps of properties that intersect a long pipeline. The maps will zoom to the part of the property which shows the intersection. The lengths of ...
5
votes
2answers
896 views

What does Scale mean in the reference of Desktop GIS or WebGIS?

I'm having trouble understanding the meaning of the concept of scale when it comes to maps on screen, i.e. either in a Desktop GIS or in a WebMap. When it comes to paper maps, the idea is very clear. ...
7
votes
2answers
13k views

OpenLayers: Use scales instead of resolutions

Venturing around in the OpenLayers source code, it seems like everything related to zoom-levels is done using resolutions. Fair enough since this related directly to screen space. I would like ...
1
vote
1answer
520 views

Relationship between scale, ppi, and map resolution

Wanting to know the screen resolution (pixels per inch) of my device, I displayed my map resolution and scale using this openlayers code: console.log("resolution: " + map.getResolution()); ...
10
votes
2answers
1k views

Surface distance on DEM between two coordinates

Given two coordinates on a digital elevation model (DEM), how do I compute the actual distance traveled between the two locations, assuming a straight line route? How will changing the resolution of ...
7
votes
3answers
391 views

How to handle display of nested polygons (census, county/state, etc) for a given map extent

My question is how best to decide which layer (from a set of nested, aggregated census polygons) to display for any given map extent in an online map. Australia's census boundaries are built from ...
5
votes
1answer
4k views

How to calculate the bounding box by a given center and scale in Android?

Given these conditions: a scale like 1:50000 the center of the viewport is 100°E, 20°N the size of the viewport is 400x600 How can I calculate the bounding box of the viewport? Update after ...
3
votes
2answers
2k views

Figuring out map scale when you know the spatial resolution of a Satellite Image?

I'm interested in figuring out how map scale and satellite pixel size (spatial resolution) are related. For example the TM or ETM+ has roughly 30m ground resolution, then, what could be the finest ...
2
votes
1answer
391 views

Python script for Data Driven Pages to run a series of DDP at once?

I have a several different polygon shapefiles that I am using to create individual maps for each polygon within the shapefile. The layout is the same for each map, the only thing that changes is the ...
4
votes
1answer
798 views

How to use scale -rule based renderer in QGIS?

I wish to render a shapefile of builindings such that at scales below 1:5000, they have a border, and above 1:5000, they do not have a border. For this, I went into layer properties, selected ...
4
votes
1answer
1k views

Dimensional analysis/conversion problem: Map scale to image resolution (dpi)

Given a map scale of 1:17,200 and a raster whose cell size is 6 inches, what resolution (dots per inch) should I choose when exporting the map to an image in order to maintain the raster's native ...
2
votes
1answer
1k views

ArcMap Text Annotations Display in Proportion to Map Scale

My question is probably of an 'easy fix' however I've been struggling with it for a while! I'm trying to set up an annotation labels for several feature classess in a map and would like them to ...
2
votes
1answer
881 views

How to Determine to world map size in pixel given this data?

How to Determine the world map size in pixels given this data? Map size of a particular area say, for example: Makati city, Philippines with bounds: Top-Right: 121.0281, 14.56497 Bottom-Left: ...
2
votes
1answer
853 views

How to show labels depending on the zoom scale and save it forever in one project?

I have got a problem in showing labels for a polygon layer : When I select "Show labels" in the layer's properties, then I select that I want to use the scaling to show or not my labels and I ...
1
vote
2answers
2k views

How do I import OS raster tiles into QGIS at the correct scale?

I have some tiles of OS raster mapping and their associated TFW georeferencing files. The GR files are in the same folder as the raster data and have the same names, ie TQ21.tif/TQ21.tfw. In QGIS ...
3
votes
2answers
1k views

How do I know the vertical/horizontal units of my DEM? I'm creating a slope using gdaldem

I'm using gdaldem to create a slope map. I can apply a scale. The default is 1. The notes say: Ratio of vertical units to horizontal. If horizontal unit of source DEM is degrees (e.g WGS84 ...
3
votes
0answers
2k views

How to use Scale tool when Georeferencing Raster in ArcMap?

I'm georeferencing a bunch of maps in ArcMap 10.0. The Shift and Rotate commands are pretty easy to use, no problems there. But whenever I use the Scale command, the image completely changes ...
3
votes
1answer
984 views

How to get correct scale values?

The scale of my map is wrong, no matter what coordinate system I use in my project. The map and all objects show the correct coordinates but the scale of the map shows nonsense and the measurement ...
3
votes
1answer
1k views

Mapserver, TMS, Scales zoom levels and how to deal with all of it

I have a whole bunch of data in my db that I need to draw at different zoom levels using Mapserver. Everything uses a 4326 SRID. My (custom) client, will fetch the data using 20 TMS zoom levels and ...
2
votes
2answers
100 views

When does a local system introduce errors in a map due to the earth's curvature?

If the extent of a map is very small, like a building plan, there is no coordinate reference system used. To which scale/size of building is that acceptable? Of course it depends on the precision ...
2
votes
1answer
579 views

importing coordinates via a csv file does not work

I tried to manually add point data via a CSV file to an empty project in QGIS 1.8.0. The points do show up all right with the correct coordinates, but already the scale is not correct (using the ...
1
vote
1answer
62 views

Digitized Map To Scale

Is it perfectly acceptable to produce a map at a scale of 1:24,000 from a database that was digitized from a 1:100,000 scale source map?
1
vote
2answers
130 views

Since upgrading to ArcGIS 10, my application doesn't rescale the map when the window is resized

I am upgrading a .NET application from ArcGIS 9.3 to ArcGIS 10.3. I've noticed that the map control behaves differently: the map no longer automatically rescales itself when the window is resized. To ...
1
vote
1answer
126 views

Dynamic scale dependency from attribute query using ArcGIS for Desktop?

If I have a feature class called roads with an attribute for type e.g. highway etc. Is there a way to setup a dynamic scale dependency on the layer based on the type of road? Like do a SQL query ...
1
vote
1answer
143 views

Why are my points being flipped or mirrored when I convert from DMS to DD?

I have a collection of crash data that provides latitude and longitude in degrees, minutes, and seconds that I'm converting to decimal degrees using: (degrees + (minutes/60.0) + (seconds/3600.0)) ...
1
vote
0answers
261 views

qgis html annotation - scale dependent rendering?

In the QGIS 2.2 map composer, I have a large map at a certain scale (let's say 1:25000) and an inset map that is an enlargement of part of the main map (let's say 1:12500). When adding html ...
1
vote
1answer
443 views

Map scale vs. map extent vs. map canvas size in Print Map Composer

Please help! I am so beyond frustrated. I am using QGIS 2.0 and when I try to create my map in the print composer, I cannot make the scale and the extent the way that I need it. I need my map to be ...
1
vote
2answers
4k views

What do I need to change to get scale bar units other than degrees?

Measurements done in QGIS on my project are done properly using whatever unit is set in: Settings > Options > Map Tools > Preferred measurements units but the scale bar decoration and scale bar in ...
0
votes
1answer
538 views

Adding a scale using SDK GXP OpenGeo Suite

Followed the tutorial using the OpenGeo suite SDK, and looking at adding a scale to my maps however the tutorial doesn't cover adding widgets only plugins. So I am not sure about how I would add ...