Use for questions which involve a GIS principle or theory and are software agnostic

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2
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2answers
69 views

Quantitative vs Qualitative heatmap

I'm having a debate with a colleague of mine over whether generated heat maps are quantitative or qualitative in nature. The underlying data source is GPS points. The GPS devices that we use are ...
2
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0answers
26 views

Do somebody know how factors as “age of data”, “scale” and others influence the precision of GIS data?

Several factors may cause imprecision in datasets. As example of such sources, we should list: "age of data", "formatting", "scale", the technique employed to create the data and others. Each of them ...
0
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0answers
11 views

Guideline on how to reference units and intervals in the legend

I often use some kind of elevation data in my maps in form of grids and contours. I never really put much attention to how to properly specify units and intervals in the legend but now polishing my ...
0
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0answers
34 views

Is it valid to resample a raster from 1m to 3 feet?

I know that in general it is not a good idea to up-sample. I am curious if it would still be be a "bad idea" with a minor change like this from 1m resolution to 3 feet? Going to 3 feet would not ...
1
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2answers
56 views

Reprojecting raster from one CRS to another?

I have a .tif raster file which is based on some projected coordinate system (for example: NAD 1983 State Plane California). I would like to export this raster as a .xyz file, but also reprojecting it ...
1
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0answers
21 views

Ideal minimal area for watershed automatic delineation using DEM SRTM

I need to do a bunch of analysis on a city using for that, watersheds . As smaller the watersheds are, better are quality of my work. Due to the vertical accuracy of SRTM DEM, I know there are some ...
0
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1answer
48 views

Removing every second row and column cells from a raster file

I have a SRTM 3 arc second topography model (.tif file). If I remove every second row and column of cells from the grid, can it be said that the model becomes a 6 arc second? Or does SRTM 3 arc ...
2
votes
1answer
106 views

What would a simple hillshade algorithm be?

I'm curious how GIS systems actually generate a hill-shade from input data like a raster DEM layer. I'd like to implement my own in software (mostly for fun/learning) but I want to start with a ...
1
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0answers
45 views

Formula for Nicolosi Globular Projection

What is the formula for the Nicolosi Globular projection? In other words, what is the function that maps the coordinate (φ, λ) on the sphere to the coordinate (x, y) on the plane? You can assume ...
1
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1answer
44 views

How is width commonly defined for areal features?

Map generalization guidelines, for instance applicable to CORINE Land Cover or Polish BDOO databases state inclusion criteria for areal features like "area should be > 250 000 m^2 and width should be ...
11
votes
1answer
131 views

How big does a circular geofence need to be for the curvature of the earth to matter? [duplicate]

I'm working on adding geofences to a mobile application. I know the proper way of calculating distance between two points on a sphere is using the great-circle or Haversine formula. I don't know if ...
-2
votes
1answer
32 views

which projection are best for large continents [closed]

which projections are best for large continents and mid-latitudes
1
vote
1answer
37 views

Calculating scale for printing on paper

I will be making PDFs with maps on them. Two pages, one a4, one a3 format. Both will print the same thing, just one is going to be larger. Question - what scale do I print on the PDF? The number. If ...
0
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0answers
24 views

Does sinusoidal projection have constant scale factors in all directions?

I know that no map projections preserves all distances. However, looking at the definition of the sinusoidal projection: y = R * phi x = R * lambda * cos (phi) , where R is the radius of earth. ...
2
votes
0answers
33 views

How do we call the plane a latitude circle is in?

I was just wondering if there is a proper term to refer to the plane that contains a circle of latitude. I know for the special case of equator, that plane is called the equatorial plane. What about ...
2
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0answers
66 views

How does geofencing work?

How does geofencing work? I am aware that it creates a sort of polygonal bubble which can execute a certain action when you pass through it, but how does it actually do that without just constantly ...
0
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1answer
150 views

Rounding Coordinates

If you want an accuracy of seven digits, should you then round to that value or simply just cut the numbers after that? Example: 51.1936137567 to 51.1936138 or 51.1936137567 to 51.1936137
3
votes
1answer
133 views

Difference between datum and ellipsoid for geodetic coordinates?

Looking at the Wikipedia page for the North American Datum, it seems to imply that the datum is completely defined by the ellipsoid, which defines the major/semi-major axes, flattening, etc. For ...
0
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2answers
133 views

How to determine objects area (size) measurement error using satellite images?

I am working at scientific paper about measuring object's size (it's area) using satellite images. I got some progress in it and need to compare my results with other scientific works. I have found ...
3
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0answers
175 views

Queen vs Rook neighborhood

Queen and rook neighborhoods are two common ways to calculate statistics for a focal cell. They are also known an Moore and (von) Neumann neighborhoods. I think a "bishop version", i.e. from lower ...
1
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0answers
24 views

How to manage unique ID's for altered polygon

I'm working with administrative boundary polygons and am wondering when to keep the existing unique ID, and when to assign a new unique ID to a polygon. For example, if District A merges with District ...
3
votes
0answers
51 views

Do locations “move” when shifting datum?

I hope that this is the right Stack Exchange for this question. I may be oversimplifying this, but I'm looking for verification in my understanding of the following: If I have a spatial dataset in 2 ...
1
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1answer
93 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?
0
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2answers
328 views

What is nontopological geometry?

I need a simple understanding of nontopological geometry. I am completely new in this area so please correct me if I am wrong. As far as I understand in topological geometry the object(say a line) ...
0
votes
1answer
33 views

Map Projection - Why don't we draw things out

I have been reading about different map projections and kind of understand where the problem lies. And also, most of the problem was that the old cartographers did not have any other tool other than ...
4
votes
1answer
160 views

How do I find/define a projection that gives me exact relative positions inside an area?

Assuming that a set of positions are all inside a 5km square area: How do I find/define a projection to reproject the positions, so that the relative positions between the now reprojected positions ...
2
votes
1answer
780 views

Measuring distances when crossing UTM zones?

I like to calculate distance between two UTM coordinates which are in different zones. Could any one point me how I can do this. I found that we can map these coordinates in to a new projection for ...
1
vote
1answer
159 views

Multi-Ring Buffer Methodology

When creating a multi-ring buffer I see two methodologies: Create buffer around feature, buffer the resulting buffer, and repeat for as many rings as required. Using the initial feature to create ...
1
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2answers
122 views

Is there cartographic convention for displaying text label of highest and lowest values in legend?

The first I have found is to have the lowest value and highest value be displayed like the legend shown below (image source) The second is to have relative numbers at the top and bottom (image ...
14
votes
3answers
857 views

Using GIS tools for non-geographical problems

Many other fields have visual/"spatial" problems that can potentially be solved with GIS tools. I know I've used GIS tools for the odd non-geographical task and was wondering how much this happens and ...
2
votes
1answer
212 views

Regarding spatial relationships, what is the Dimensionally Extended 9 Intersection Model (DE-9IM)? [duplicate]

In plain English what is the Dimensionally Extended nine-Intersection Model (DE-9IM)? What is the meaning of each row/column in the matrix? How can I use that information to build a relation ...
1
vote
1answer
54 views

Locating Moon in Sky from Earth

I am working on project which need to find moon location from a specified lat, long on earth. So basically info I am having is Lat,Long and Timezone. Format of the moon location Info? So first in ...
3
votes
3answers
664 views

Which rule to follow for defining an intersection as an ordered pair of streets?

Explanation Sometimes, for the sake of simplicity or speed, I need to list a location as a pair of intersecting streets. Let's use Luckie Street Grocery Store in Atlanta, Georgia as the example for ...
0
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0answers
133 views

When to use DBMS instead of System Files for Spatial Data Storage?

I'm having trouble deciding when it is best to use a DBMS instead of System Files for storage of Spatial Data. Are there any specific guidelines and reasons for when one method is preferred over the ...
2
votes
2answers
229 views

Measuring tool shows different measurements for same building in two different map documents?

So I have two map documents with two different Coordinate Systems set for the layers but using copies of the same shapefile. Map 1: Coordinate System: ...
1
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0answers
44 views

Are ellipsoid and datum the same? [duplicate]

Are the datum and the ellipsoid the same? What is a Datum? The Earth is shaped like a flattened sphere. This shape is called an ellipsoid. A datum is a model of the earth that is used in ...
1
vote
0answers
75 views

Internet mapping UX design strategy: Separate desktop and mobile sites, or one site fits all?

I searched GIS.SE for "Desktop vs. Mobile" and didn't get anything helpful, so I guess I'll be the one to ask. Question: With respect to Internet mapping applications, is it better to have separate ...
6
votes
1answer
2k views

Raster vs Grid vs Lattice terminology?

I have a question about GIS terminology - what is the difference between grid and raster and grid and lattice - in theory?? I thought, that raster is regular network and value is in the cell and the ...
22
votes
4answers
6k views

Difference between node and vertex in GIS?

In graph theory the term of node and vertex are equivalent, but sometimes in the GIS world the nodes and vertex are mentioned in the same context. I was wondering what the difference is? Node: can ...
3
votes
3answers
185 views

Can a single raster pixel hold more than one value?

Can a single pixel of a raster hold more than one value?
1
vote
1answer
2k views

How to calculate the size a bounding box?

What formula could I use to calculate the size in Kilometres of a bounding box based on a given Southwest latitude/longitude and a Northeast latitude/longitude points? The bounding box format is ...
1
vote
1answer
69 views

Do transfer edges add to the distance cost of a route?

Transfer edges are commonly used in a network dataset to carry a time cost in one direction only (either to-from or from-to). This is fine if the impedance used is time, i.e. find the route that will ...
3
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0answers
344 views

Linear Referencing Methods: Station Equation origins

DEAR PEOPLE FROM THE FUTURE: Here's what we've figured out so far… I am working in the pipelines field, and I get in touch with the concept of the linear referencing methods, specifically with ...
7
votes
4answers
138 views

Selected Literature on coordinate transformations?

I am looking to hone my skills in the theory and the mathematicas involving the projections systems, projection transformations ( from xy to uv, φλ and vice versa). Can you share the ...
2
votes
1answer
38 views

Is it better to define object properties or layer properties?

I have a question, but it is difficult to phrase. I am picking up GIS methods as I go, and I have run into this problem frequently. Please excuse me if I am in the wrong place. When organizing ...
2
votes
1answer
152 views

What are the geometric principles and GIS techniques that I can use to generate a postcode coverage of my city at street scales?

Postal codes of Brazil and another countries are oriented to distribution logistics, and improvement of reliability in writing the postal addresses; but without much concern for the spatial ...
6
votes
1answer
260 views

How to store route names of a stop belonging to multiple routes

I've been reading the ArcGIS help files on route analysis to gather more information on what attributes are stored with Stops. Maybe I've stared at the screen too long, but I cannot seem to understand ...
11
votes
3answers
376 views

Does Earth's magnetic field affect any datum definition?

I had an interview last week. One very interesting question was "does earth's magnetic field affect any datum definition?" I was sure it does not for geocentric datums. But I thought maybe the ...
6
votes
1answer
4k views

Polygon Centroid Options and Appropriateness (FeatureToPoint, Labels, etc)?

I've found a couple of other Stack Exchange questions related to this, but they were not satisfying. For example: How does ArcGIS Desktop calculate INSIDE point for Feature to Point? does not tell ...
21
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7answers
2k views

Spatial reference for dummies?

Can anyone recommend a good reference or tutorial that explains the principles of spatial references, projections, and coordinate systems? We are a small team of programmers working with GIS ...