I'm building a Florida county map using geoJSON. I downloaded 67 county files and combined them in Cartodb. The current file is huge: 4MB with thousands of lines of code, especially in the coordinates. Here's what it looks like. The map works, but it's slow to load on the browser. I've seen other JSON files that are smaller and easier on the browser. Is there a way to shorten the code so they still show the counties on my map? Maybe removing a majority of the coordinates?
you can use TopoJSON which is a topology encoding extension to GeoJSON.
"Rather than representing geometries discretely, geometries in TopoJSON files are stitched together from shared line segments called arcs."
read more: https://github.com/mbostock/topojson/wiki
repo:
https://github.com/mbostock/topojson
Not trivial. One problem is that you have multiple counties, using the same coordinates so they fit together (so the east of county A and the west of county B are identical).
You can analyse your data: If you have a line A->B->C, you can calculate how the area changes if you emit point B. Remove points as long as the total change in area is small. Make sure that if you remove a point in one county it must be removed in the other counties as well. Then you may check how much change you get by leaving out the last decimal of each point. Again, the same point must be changed in the same way in all counties.
There is a Free API to obtain US County in GeoJson format..u can add multiple counties(since u have a list)
https://www.mashape.com/vanitysoft/boundaries-io
Example query:.../rest/v1/public/boundary?and=true&county=Washington+County&state=MD
please note that some zipcodes do not fall within a county.
Related
I have a GIS Map in which I uploaded a shape file with the zipcodes of a given region. I want to generate random points inside these regions, but I haven't been able to get the region element with the zipcode String name. I tried using the searchRegionFirst and searchRegion functions with the region name loaded from the shape file but they end up finding other places not related to the zones I have. Is there a way to get the region by its custom name?
Thank you
I could solve it, I just leave the question in case someone runs into the same problem. So just go to the project panel and under the main->presentation->level->map you can find all the GISRegions created. Just select them all with shift and with the right click you can find the option to create a Collection of the GISRegions. Then just use this collection to iterate through the zones.
I queried some data from UNHCR for a refugee resettlement project on Syrian resettlement trends from 2010-2020 in four specific countries (Canada, France, Germany and USA) and have it saved as a .csv file. I am wondering if anyone knows if it is possible to create a feature class associated with the Country name or ISO-3166 alpha 2 code (for example, France or FR) to be a polygon coinciding with a country. I have been able to save this .csv as a point feature class and have looked on the ESRI help forums which give instructions however each time I import the file to ArcGIS Online it only displays as a point feature. If anyone has any insights or workarounds it would be greatly appreciated! I also have access to ArcGIS Pro if needed.
You will have to find a polygon feature class with the country boundaries to join the CSV data to (maybe see here https://gis.stackexchange.com/questions/23028/getting-polygons-of-all-countries-and-iso-3166-2-subdivisons). It sounds like the CSV just has one point (probably a centroid of the country) in it.
I also recommend you join https://gis.stackexchange.com as well to ask about the joins etc
I'm just trying to figure out how to create world file. I saw some explanation but I notice world file having the easting and northing values but not the zone value. So how the location of the map will be identified, or I'm missing something.
Thanking you.
The world file does specify numerical geographical location for an image, but it unfortunately does not contain any information about what coordinate systems is used.
Such information typically comes in a separate file with extension .prj and is defined usually with the WKT standard and via a unique EPSG code of the coordinate system.
To simplify the search for coordinate system definitions we created an online tool:
http://epsg.io/
There you can use simple search phrases and preview position of any coordinates on a map - and also download the .prj file mentioned above.
Because you have tagged your question with "maptiler" I expect you want to cut the map tiles from your geodata and world file with the MapTiler software.
The coordinate systems can be specified directly in MapTiler easily. See http://www.maptiler.com/how-to/coordinate-systems/
I am trying to add a shapefile that is a map of Manhattan wards and then plot some latitude-longitude data points over this map. I'm new to ArcMap and GIS in general.
Here is exactly what I am doing:
I have a shapefile that shows Manhattan wards when I "Add Data" it into ArcMap. I then go to Geoprocessing -> ArcToolbox -> Data Management Tools -> Projections and Transformations -> Define Projection. I then input my .shp file and select NAD 1983 State Plane New York Long Isl FIPS 3104 (US Feet) for the coordinate system. After I do this, my shapefile displays just fine.
I then "Add Data" a .csv file which contains addresses and the latitude and longitude for these addresses. I then right-click on this layer and select "Display XY Data...". I then make the "X Field" latitude and the "Y Field" Longitude and use the same coordinate system as mentioned above. However, the points never display. I still only see the wards shapefile displayed. Both layers are present in the Layers menu, but only one is actually being displayed.
Alternatively, if I restart ArcMap and add the points first and display the XY data, I see that the points are displayed. After I add the shapefile, the shapefile does not display. I only see the points. It seems I can always display one thing but not the other.
Any thoughts on why this is happening?
I am using ArcMap version 10.2.0.3348 on a Windows OS.
I assume you are trying to overlay different spatial reference systems without telling arcmap which ones you use, so it cant reproject them to fit together.
When you say "latitude" and "longitude" you normally mean a geographic coordinate system like WGS84. Whilse X and Y often refer to a projected coordinate system like NAD. You defined NAD for both layers...I think you should define a geographic coordinate system for your CSV File, if it really contains geographic coordinates.
ArcMap uses the spatial reference system of the first layer which is added as the display SRS (you can change this afterwards for sure), thats why you saw your shapefile first and after restart and adding the points saw the points first.
If every layer has its SRS defined correctly, ArcMap will reproject them automatically to fit your display SRS. If you define the wrong SRS for one layer, Arcmap will do nothing for sure, because there is no need to reproject a NAD layer to NAD (although the coordinates have a completely different value domain and your points get drawed somewhere else....check this by right clicking on the CSV layer and "Zoom to Layer (extend)".
To make it more complicated: Because NAD83 and WGS84 rely on different geodetic datums, you have to transform. You find a predefined set of transformation parameters when you right click on "layers" in the "table of contents" on the left and select "properties". On the "coordinate system" sheet you see the "Transform" Button where you can select the transformation parameters which should be use to get from NAD83 to WGS84 and vice versa. A more detailed description can be found at this GIS SE
I am trying to obtain accurate site geometry for a particular location in Autodesk Revit. The site in question is located near 19621 Waters Road, Germantown MD 20874-0000. The problem is that I can only import CSV or other comma delimited text, or a CAD format, into Revit, but height data for the region at the nessisary resolution is only available from USGS mational map thingey in ArcGrid, GeoTIFF, GridFloat, and BIL_16INT formats. I am working on a computer where (because of systemadmin stuff) I can't run any unapproved executables or anything, and my home computer doesn't have Windows, only Ubuntu. Does anyone know a way to convert the data to what I need, or know of a better whay to obtain this?
If your ARC GRID is an ascii file (not binary), don't worry about .asc and just open it in Notepad.
You will find there words xllcorner, yllcorner and cellsize, and values for cell centers. Keywords xllcorner and yllcorner are coordinates of the low left corner of the grid. (And you need to know what is the coordinate system of the file and if it is the same which you want to import as csv.)
Then you can calculate (for example in Excel) the coordinates of each cell center using cellsize. And then write all this in three columns x,y,value into a text file name.csv.
I have a routine that did thins using google earth, VBA and excel... You have to install the google earth developers package but it works pretty well- grabs images off GE and coordinates it with revit VIA a CSV file.
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