# Tag Info

## Hot answers tagged measurements

14

The measure tool does not need any extension. However, the coordinate system of the data frame needs to be defined before you can use it. right-click on the data frame to set its properties.

10

Here is a paper that may help in beginning to drive your selection of distance measures. Take note of table 1 (pg. 4), copied below. On geodesic distance modeling and spatial analysis (2004) - S. Banerjee I would suggest that if you intend to use inter-UTM zone distance computations you should be using a geographic measure. Likewise, the spatial ...

10

Assuming your stream polylines do not already have an attribute that states which watershed they belong to, you can run Identity (Advanced license only) or Intersect to get that attribute assigned in a new feature class. This also makes sure your streams actually break at the boundary rather than continuing through multiple areas. Then you can open the ...

8

If you're home-brewing in the browser, you can get a "circle" (it will not be round on the screen due to your projection; rather approximated by a polygon w/ as many points as you care to draw), use a the direct form of geodesic calculations: given a point, a direction (azimuth), and a distance it gives you the resulting point. Gory details: http://en....

8

Accuracy of calculated results depends on a number of discrete processes, which can all compound inaccuracy in the final dataset. The importance of Metadata in this situation, is it can be used to explain error and even identify steps error is introduced. The most important thing is to understand that ground truthing your results, if performed correctly ...

7

Your suggestions sounds fine. Also every geometry object has a distanceTo() function which can be used like: geometry.distanceTo(anothergeometry) EDIT: After more thought and testing the example, i think it would be easiest for you add new layer for labeling purposes. Possibly a layer of just points which you would set the labelXOffset and ...

5

Here is copy-paste from one of my old applications. EDIT: I modified getCustomLength, so it should work with different coordinate systems. Fiddle: http://jsfiddle.net/A78Zu/ measureControl = new OpenLayers.Control.Measure( OpenLayers.Handler.Path, { immediate: true, persist: true } ); measureControl.getCustomLength = function(...

5

The CRS of your project is probably set on a geometric CRS like WGS. Try setting it to the same one you used for the shapefile.

5

A little theory: When using a geographic (non projected) coordinate system, such as WGS84, all measurements which are made using planar geometry (calculations on a plane) are wrong. The bigger the area, the bigger your error. To have precise measurements on the ellipsoid, qgis would need to implement great arcs, etc... QGis is suggesting that you project ...

5

The easiest way to calculate shape length is to import your polylines into a file geodatabase. Once you import your shapefile as a featureclass, length is automatically calculated for every feature. If you are interested in calculating shape length within a grid, first run Intersect which will split the polylines into segments within grid. Then Dissolve ...

5

The best way I can think is to get two UTM points, convert them to Lat/Long, and compare their geodesic distances to their UTM pythagorean distance. E.g. Take a point from this example: The CN Tower is ... in UTM zone 17, and the grid position is 630084m east, 4833438m north. So if we take A (17n 630084 4833438) and move it 30 km east, we get B (17n ...

5

All the measurements are always returned in the units of chosen CRS. WGS84 is defined in degrees of latitude or longitutde, thus it returns results in degrees. If you want to obtain results in meters, you have two options: Start using geography type Reproject your data into national coordinate system defined in meters

4

@ MaryBeth - You have valid concerns, It probably is not ever going to be as easy to "draft" in arcmap as it is in autocad, or microstation, or "Their/Your CAD System Here". **EDIT: ** what's new There are some SUPER nice features however that I am beginning to really love in desktop 10. ESRI has come a long way to making or facilitating a (used to be ...

4

If you go to Settings -> Options there is a Map Tools tab, on that tab you change your preferred units for the measure tool from meters to feet.

4

After you activate the Measure Tool, press the Space Bar to disable snapping. There should be no lag.

4

A useful tool is the integrate tool, which will be easier than the create centerline tool. Make sure that you use this tool on a copy of your dataset or in an edit session (in case your tolerance was too large) because otherwise you cannot go back. Also note that you can set an tolerance (in the environment settings) when you use a tool like "dissolve" in ...

4

I am afraid that the answer is no: what you mean to do is correct but it will not work like this in ArcGIS with Near. From the help, you can read that : The distances calculated by this tool are in the unit of the coordinate system of the input features. If your input is in a geographic coordinate system and you want output distances to be ...

4

Rachel: First you need to convert the lines to LR Routes with assigned measures. Each line should have a Field with a unique ID value of some kind that means something to you. That field will be used as the Route ID. If the lines have to start at 0 for both ends, depending on the camera referenced as the start then you should make the Route ID something ...

4

The projection that you use will distort the properties of your objects. You can select your projection to preserve the shape, the area OR the distances but not all at the same time. If you want a specific feature to be preserved, you need to select a projected coordinate system with this property (conformal for shape, equal-area for area or equidistant for ...

4

Lines and polygon dimensions are never exact and subject to the limitations of the feature class resolution and tolerance. Infinite precision is not possible and as a result these settings tell GIS to consider measures below those levels as "close enough" to exact measurements. There is no setting for absolutely no tolerance and infinite resolution for ...

3

You can use the 'Calculate Geometry' (Right click on an field in the attribute table) tool to determine the area of each polygon and then use the 'Summary Statistics' (in the Analysis toolbox) with the owner name as a Case field and the area field set to sum will produce a table that shows the total area for every unique entry in the owner name field. Here ...

3

Qgis wants you to define a projection system to be used in your project. It wants it so if you're going to import something from the "real" plane (remember that the earth is spherical) to know where it should go in the Cartesian plane. There are numerous projection definitions ready to be used that were tailor made as solutions for specific problems. Proj4 ...

3

OpenLayers only allows for drawing circles using planar distances To get a geodesic circle, you could use the buffer operation in ESRI's geometry service. ...if unit is linear such as feet or meters, geodesic buffering is performed A freely accessible one is available here.

3

Are you definitely working with a projected shapefile? If the shapefile is in ArcMap, right-click on the shapefile, click on Source and look to see that is in a Projected Coordinate System rather than a Geographic Coordinate System If it's geographic, go to Data Management Tools ->Projections and Transformations -> Feature -> Project. Then add the ...

3

right click on the area column and hit calculate geometry. select the correct unit. and the area.

3

Edward, I'm going to answer your 2nd question 1st. "Do I need to open all the other files?" The .shx, .sbx, .dbf etc.... all hold information that compliments the .shp file you have. When you open the .shp in QGIS, it will automatically read the relevant information form each of those files. It is very important that if you move the .shp to another folder,...

3

As you have yet to clarify if your lines overlap exactly or just are parallel lines, I'll give you two ways of doing it. 1: Exactly overlapping lines can be merged together with the Dissolve function. Make sure you uncheck the "Create multipart features" checkbox. 2: If your lines are just close to each other you can buffer them to polygons (use a buffer ...

3

I think you are going to have to break (as a node) the road at the polygon edges to do this in vector space. Use Identity Tool in ArcGIS and this should do the trick. Just option that is something like Just ID Remember to recalculate lengths in the attribute table after the identity (just to be sure) It will add the polygon details (in this case thee ID)...

3

From ESRI: "WGS 1984 Web Mercator and WGS 1984 Web Mercator (Auxiliary Sphere) use a conformal projection that preserves direction and the shape of data but distorts distance and area. Published in 1569 by Gerardus Mercator, the Mercator projection was created for use in navigation. A straight line drawn on a map in this projection provides a bearing by ...

3

If you need high accuracy distances, or "ground" distances, you need to convert your UTM "grid" distances (which you do indeed calculate via pythagorous) using a combined scale factor. This removes the distortion introduced by the combination of (a) reducing the horizontal distance at its elevated (above the ellipsoid) position on the earth and (b) ...

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