1k views

Measurement accuracy for small distances - geodesic vs. planar UTM WGS84

Does anyone know how accurate geodesic measurement is compared to planar measurements in UTM WGS84 for distances below 15km? We'd like to inform our users about measurement accuracy when using tools ...
186 views

Are perpendicular lines still perpendicular after converting from UTM zone 15 to 16 (or between two neighboring zones)?

I want to convert a square polygon that is close to the edge of UTM zones 15N and 16N. The polygon's coordinates are in UTM 16N, but it is spatially positioned in the UTM15 area. My question is that ...
91 views

how to calculate area if it is falling in two utm zones [duplicate]

I am using ArcGIS 10.1. How do I calculate an accurate area measure for a polygon, where portions of it are falling in two zones, i.e. UTM ZONE 44 & 45 (India)?
409 views

Pseudo code to correct Geographic points for UTM Easting distortion on Web Mercator Projection

I have chosen to use a Web Mercator projection system for: Use of Tiling system for low memory usage Accessing only one site/area at a time Reuse of Google Tiles - for many sites In some cases I ...
239 views

Is nearest search done on Euclidean plane accurate

I am writing a program which will find all the points within 1km. I am planning to to do this on a Euclidean plane as my database only supports Euclidean plane or sphere indexing (http://docs.mongodb....
778 views

How does the projection of a dataset affect the results of spatial analysis?

I am planning on conducting a multi-criteria-analysis with a number of different source datasets. A number of the datasets are found in different coordinate systems and projections. Do I need to ...
1k views

Is it possible to calculate area of polygons from GPS points without POSTGIS

I am new with GIS. Assume we use the UTM30N coordinate system. Is it possible to calculate an area (say a square box) by the 4 given points? (assume the points are in order, and the coordinates are ...
402 views

Albers Conic versus State Plane Zone in terms of accuracy?

I'm trying to determine if an Albers Conic (Alaska Albers) is suitable as a projection for a corridor 800 miles long by 50 miles wide, that goes from the north coast of Alaska to the south coast. ...
522 views

Changing projection for field calculator

I've just succeeded in getting the area of a polygon using field calculator. The polygon was drawn on a Google hybrid aerial photo. There are no units given in the calculation and I assume the area ...
1k views

How much error in a transformation?

I've been working in GIS for about a year and have a functional grasp of Projections and Transformations from within ArcGIS (10.0). Geosoft Oasis is another program we use. In working with our data ...
4k views

Distance measurements across UTM zones: use geographic or planar approaches?

I have a survey grid spread across 3 UTM zones (36N, 36S, 37S). I want to find the nearest (or shortest) distances of the centroids of these grids to roads and various points between. It seems like ...
4k views

What is a good projection for the whole of China (with units in meters)?

I get some GPS results which lay in China with WGS84 coordinate system, and I need to choose a projection to reproject for. First I chooses the UTM projection, but I find the results lay in ...
1k views

An example Tissot ellipse for an Equirectangular Projection?

I am trying to calculate distortion of an equirectangular projection via Tissot indicatrices. I have tried following the directions on this post (among other things) but it is beyond my understanding ...