# Tag Info

## Hot answers tagged scale

46

If you are designing a map you plan on overlaying over google maps or virtual earth and creating a tiling scheme then i think what you are looking for are the scales for each zoom level, use these: 20 : 1128.497220 19 : 2256.994440 18 : 4513.988880 17 : 9027.977761 16 : 18055.955520 15 : 36111.911040 14 : 72223.822090 13 : 144447.644200 12 : 288895.288400 ...

21

To help you understand the maths (not a precise calculation, it's just for illustration): Google's web map tile has 256 pixels of width let's say your computer monitor has 100 pixels per inch (PPI). That means 256 pixels are roughly 6.5 cm of length. And that's 0.065 m. on zoom level 0, the whole 360 degrees of longitude are visible in a single tile. You ...

17

Not that easy. Given the projection, the size of the tile pixels depends on the latitude of the area you're interested in. Then in terms of transforming tile pixel size in screen pixel size, it depends on the screen and the resolution the data is displayed, the dpi your screen is using.

16

In order to use scales on your map: Set only the 'scales' option. Do not set maxResolution, minResolution, maxScale, minScale, numZoomLevels, or any other scale related property. Set it to an array of scale denominators (or scales). Configure a unit: note that for meters, this should be 'm', for degrees, 'degrees', etc. You can set a maxExtent. Do not set ...

12

This document presents an algorithm to do that: Harrie, L., Sarjakoski, T., Lehto, L. A variable-scale map for small-display cartography. In: Joint International Symposium on GeoSpatial Theory, Processing and Applications (ISPRS/Commission IV, SDH2002). Ottawa, Canada, july 2002 An example: EDIT: This kind of representation is quite old. See the plan ...

11

As the scale is a ratio, it doesn't have units itself. You can measure whatever you like on the map - one inch, one foot, one double-decker bus - and it will represent 6000 of the same unit in reality. To give the scale in mixed units, you just have to know what 6000 inches are in feet - OnlineConversion tells me it's 500 feet - so you'd have 1 inch = 500 ...

10

I found this response - written by a Google employee - this would probably be the most accurate one: This won't be accurate, because the resolution of a map with the mercator projection (like Google maps) is dependent on the latitude. It's possible to calculate using this formula: Meters per pixel = 156543.03392 * Math.cos(latLng.lat() * Math.PI / ...

10

Degrees of longitude get smaller as you move away from the equator, eventually going to 0 at the poles; degrees of latitude don't suffer the same fate (looking at the latitude and longitude lines on a globe will make this clearer). Projecting your data to a coordinate system should solve the problem, because feet and meters don't change in size as you move ...

8

There is such a table in the documentation of the Virtal Earth Tile System from Microsoft. But as said by GuillaumeC the values depends on the latitude and on the screen resolution. The table gives values as measured at the Equator and at a screen resolution of 96 dpi. PS: Not sure of that, but the zoom levels by Microsoft might be shifted by 1 in ...

8

Straightforward authoritative correct answer: 591657550.500000 / 2^(level-1) it gives you the table above, entering the zoom level. Try it live on jsfiddle.net Because the question is only for Google MAPS, not EARTH, the OP doesn't care about 3D geometry. Google maps are ALREADY flattened so 1 pixel is always the same distance (in DEGREES, which is what ...

8

If you don't have this capability built into your GIS, but you can perform some basic grid operations ("map algebra"), there is still a solution. The calculation comes down to finding the slope of the route at every point. If you knew this exactly, with no discretization error, you would integrate the secant of the slope. On a grid, the integral is ...

7

SAGA GIS has a module for this: Interactive profile http://www.saga-gis.org/saga_modules_doc/ta_profiles/index.html The resulting points will contain the distance and the overland distance. If the DEM has a coarser resolution your overland distance will always be a bit lower (unless you have strange border conditions), but in reality this difference is ...

7

How you'll go about solving this problem really depends on the case, and how important the actual topology is to you (versus just the visuals/rendering time). Since your final goal is to generalize coastlines, you may find some ideas on generalization useful. One approach uses buffering, as seen here. I also had a similar problem a while ago and detailed my ...

7

As @StephenLead said, ArcMap will Reproject your datasets on-the-fly. What is most critical is that each of your Datasets have the appropriate Coordinate System set beforehand. The other critical item is that you set the Coordinate System of your Data Frame. There are differing opinions as to what this should be set to, but a good rule is to set it to ...

7

Ok, with some initial issues cleared out the task is relatively simple. Scale, prepresented as f.ex 1:50000 means that one unit on the map corresponds to 50.000 units in the real world. For a paper map printed a scale of 1:50000 this means that 1 meter on the map corresponds to 50.000 meters in the real world, or to make it easier: 1 cm on the map ...

7

Assuming you are talking about a map of the world in Mercator Projection, Something like this: Then You should know that not all pixels will represent the same area. There is a large amount of distortion as you go towards the poles, the area represented by each pixel will decrease as you go towards either Pole. Tissot's indicatrices show a good visual ...

6

Your screen is probably running at 96 DPI, not 72. Computing scale as a ratio of 1:n is a risky business at best with a web map. If your map is being displayed on an average monitor, you can assume 96DPI. But that will be wrong on (say) a mobile device, or a projector, or a 19" LCD running at 640x480 resolution, etc. It is better to produce a scale bar ...

6

You could do it by defining your own projection; Copy your current projection file Open the copied file Under Linear Unit select custom Enter the number of metres per unit (eg, 10m for a pool) Save this projection Change the projection of your data frame to this new projection Add your scale bar to the layout - it will have Unknown Units, but you should be ...

6

I do not think you can do this in ArcGIS 10 without having copies of layers ontop of each other in the TOC with different drawing scales set. It would be nice if you could set different symbology classes like you can do for labeling. Below is a thread that is similiar to yours. http://forums.arcgis.com/threads/23529-Change-Feature-Symbology-at-different-...

6

Do you have your "backdrop (raster)"? If yes, then there is two options: it is georeferenced (in some non-earth coordinate system). Then everything is ok and you have just to use it with your vector data (if you have it already) or draw vector "polygons that will represent the rooms" using your raster as a background layer. In first case may be you will ...

6

You have to decide whether you want to enter coordinates in lat/lon, or from a background map with a projected CRS (e.g. in metres). For the first choice, you have to set the target CRS to WGS84 (EPSG:4326), and don't mix up lat and long values. For the second choice, the target CRS must be set to the same CRS as the project CRS. This can be different from ...

5

Radius @ Equator 6,378,137 meters exact (WGS-84) Circumference at Equator = 40,075,017 meters (2πr) Zoom level 24 uses 2 to the 32 power (4,294,967,296) pixels at circumference. Equatorial Circumference / 2 32 = .009330692 meters per pixel Unit at Latitude = (Cosine of Latitude) X (Unit at Equator) Zoom level doubles each increment. 1 foot (...

5

You should prepare different generalized versions of your data set for "full planet" zoom levels down to close-up zoom. A classic generalization algorithm is Douglas-Peucker algorithm. You'll have to connect the points to coast lines first if you haven't done that already.

5

The simple answer is no. You are right in adding multiple layers referencing the same GIS Resource is the way to go. In addition to this if you were to have the 2 resultant layer in a Group Layer then you can control them as if they are a single for some things. This is the workflow I have always used, and one I also use for the generation of Map Services as ...

5

This is a really interesting question, especially in the context of today where the quest is usually for more detail, higher resolution, etc. To directly answer your question, I think you are performing the exact correct operation. As I see it, the reason for generalizing a layer is to reduce the size and complexity, for performance reasons. This might be ...

5

Under the layer properties>labels tab you can setup multiple labeling classes (under the Method drop down) for your labeling scales. Labels can be rendered by query using the SQL Query button for each class. You can also use the Scale Range button to show or not show a certain class within certain scale ranges.

5

It is the scale at the equator.

5

You must set the Project CRS to a projected CRS, for example the UTM zone for your part of the world. Thats different to the layers CRS, which might remain in degrees. Measurement tool and scale bar look only at the project CRS, as long as on-the--fly-projection is enabled.

5

I was involved in a lot of similar work in the past but with stone decay on buildings. Here are some references on that work which you may find interesting (if a little old now): Ball, J; Young, M E (2000) “Mapping The Decay & Weathering Of Stone: A Technique For The Assessment Of Large Numbers Of Buildings”,in Choi, S and Suh, M (Eds.) Proceedings ...

5

If you want a 1:50K map displaying an area 30 miles wide then your map will need to be 0.0006 miles wide, or about three feet, or over 3600 pixels at 96 DPI (typical computer monitor). You need to explain to your client that you can show either a desired area or a desired scale but you can't do both at the same time because you generally cannot control the ...

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