If i have a grib2 file that contains information for whole world (for some parameters) and I want to extract data from it using wgrib2 based on latitude and longitude given by user (client software to server). I tried following command but I am getting complete grib2 file only:
wgrib2.exe input.grb -undefine out-box 10:90 -10:10 -grib output.grb
Please tell me where am I going wrong? Thanks.
This is still the top hit on Google, so even though it is a bit old, here is a more detailed explanation.
First, you need wgrib2 from the National Weather Service Climate Prediction Centre. (The installation of that is straightforward, but not too well explained. See this page, or this gist for help.)
Next, you need to use the lola function (for LOngitude-LAtitude grid).
You need to give wgrib2 several arguments:
the grib file that has the data
the longitude information:
the longitude of the southwest corner of your bounding box
the length of the bounding box in degrees
the spacing of the points in this direction
the latitude information, the same as above
the latitude of the southwest corner of your bounding box
the length of the bounding box in degrees
the spacing of the points in this direction
the file name to write to
the format of the file to write (either bin for binary, text for simple text, spread for spreadsheet format, or grib for grib2).
For example:
wgrib2 input.grb 220:100:1 20:50:1 output.grb2 grib
will create an output file that covers north america (220 E - 320 E; 20 N - 70 N) at 1 degree intervals in both directions.
Rob
I used the following command to extract information from grib2 file.
wgrib2.exe input_file.grib2 -lola LonSW:#lon:dlon LatSW:#lat:dlat file format
assuming that we are having following co-ordinates for selection:
Top: (x0,y0) (x1,y0)
Bottom: (x0,y1) (x1,y1)
"LongSW"=x0, #lon = (x0~x1), "LatSW"=y0, #lat = (y0~y1).
and dlon and dlan can be kept as 1. 'file' is the output file name and format can be grib, csv, text etc.
Substitute above values in the command shown above and you should get the answer.
If your chosen longitude was 360 and latitude was 90:
wgrib2.exe input_file.grb2 -lon 360 90 > output_file.txt
I think you can also use cdo directly on grib for this
cdo sellonlatbox,lon1,lon2,lat1,lat2 in.grb out.grb
If the grib file is on a reduced gaussian grid you may need to specify that you want a regular lat-lon output. I usually convert the output format to netcdf myself using "-f nc" as I find it easier to process in other software.
Related
I want to use Google Data Studio to visualize the location of NGO´s in Europe. Some of these share the same HQ Location in the Data e.g. Italy Rome. Idea is to transfer these into Lat,Long coordinates and slightly manipulate the values to show them with their name in the GMaps bubble diagram. The original data is unfit, because the digram cannot display multiple tooltips/names for the same location.
I have been following this guide https://michaelhoweely.com/2020/05/04/how-to-build-a-custom-google-map-in-data-studio-using-google-sheets-and-geocode/ to do the Geo Coding of the locations.
Problem is that the Geo Chart goes blank if I choose Lat,Long as the location dimension. Even the original data (not modified by me) will cause the same issue.
GDataStudio_Lat_Long_Vis_Issue
Any idea of what I am doing wrong here or having a better idea of how to do the visualization?
You also have to make sure you change the type to GEO, as it sometimes defaults to ABC or numeric.
It may help to concatenate the latitude and longitude values to follow the WKT format, as shown below.
CONCAT(<longitude_column>, ", ", <latitude_column>)
In the current state, the latitude and longitude are reversed, so the error is probably caused by each value exceeding the default range for latitude and longitude.
I have a data where at one latitude and longitude multiple shops are located.
For Example.
Latitude Longitude ShopId Type
6.24458 50.001756 101 Saloon
6.24458 50.001756 102 Groceory
6.24458 50.001756 103 Pharmacy
6.24458 50.001756 104 FishMarket
When on map I am plotting using above latitude & longitude I am getting single mark. And when I hover the mark I am getting single shop details but I want 4 marks and on each mark it should show respective shopid and Type.
I am new to Tableau and not able to figure out how to do it.
You are likely getting 4 marks displayed at the same location. So when you click on the mark you see, then you are only selecting the top mark. You can verify this by dragging over the mark to select all the marks within a selection rectangle. If you then, right click and view data, you should see all 4 marks.
Another thing that can help when you have overlapping marks, is to make the marks partially transparent and add a border around the marks. Both options are available by clicking on the Color button on the marks card to get to the advanced color settings.
If this is not the behavior you want, you have a couple of options. One easy approach is to add a little random noise to each latitude and longitude (called jitter). Adding a little jitter makes the marks visible, although the size of the jittering depends on your data and scale. Jittering is especially useful if all your points are geocoded to the same situation - say if every building with a Los Angeles address is treated as if it is located at city hall. In that case, the geocoding distorts the data to a degree that jittering is just fine.
The undocumented RANDOM() function is an easy way to add some jitter. Excel and Hyper Extracts support RANDOM() among other data source types. It returns a number between 0 and 1.
The other options involve treating your coordinates as continuous dimensions instead of measures, and then using some other visual attribute size, color etc to indicate the number of items at each location. It is often useful to combine nearby items with some sort of grid or hex bin function -- In this case, instead of adding random noise to each coordinate, you round or truncate it in someway to effectively snap points to a grid. The ROUND() and HEXBINX() HEXBINY() functions are useful here. When using this approach, be sure your packed coordinate fields are continuous dimensions and have the appropriate Latitude or Longitude geographic role.
Finally, take a look at the density mark type. It can make visual heat maps, either working with exact data points or grid packed points.
I am using a therm-app camera to take infra-red photos of bats. I would like to draw around parts of the bat and find the hottest, coldest and average temperature and do further analysis.
The software that comes with the camera doesn't let me draw polygons so I would like to load the image in another program such as MATLAB or maybe imageJ (also happy to use Python or other if that would work).
The camera creates 4 files total:
I have a .jpg file, however when I open this in MATLAB it just appears as an image and I think it is just opening as a normal image, not sure how to accurately get the temperatures from this. I used the following to open it:
im=imread('C:\18. Bats\20190321_064039.jpg');
imshow(im);
I also have three other files, two are metadata (e.g. show date-time emissivity settings etc.) and one is a text file.
The text file appears to show the temperature of every pixel in the image.
e.g. (for a photo that had a minimum temperature of 15deg and max of 20deg it would be a text file with a minimum value of 1500 and maximum value of 2000)
1516 1530 1530 1540 1600 1600 1600 1600 1536 1536 ........
This file looks very useful, just wondering if there is some way I can open this as an image, probably in a program like MATLAB, which I think has image analysis so that I could draw around certain parts of the image (e.g. the wing of the bat) and find the average, max, min etc.
Has anyone had experience with this type of thing, can I just assign colours to numbers somehow? Or maybe other people have done it already and there is a much easier way. I will keep searching on the internet also and try to find out.
Alternatively maybe I need to open the .jpg image, draw around different parts, write a program to find out which pixels I drew around, find these in the txt file and then do averaging etc? Or somehow link the values in the text file to the .jpg file.
Sorry if this is the wrong place to ask, I can't find an image processing site on stack exchange.
All help is really appreciated, I will continue searching on the internet in the meantime.
the following worked in the end, it was much much easier than I thought it would be. Now a big fan of MATLAB, I thought it could take days to do this.
Just pasting here in case it is useful to someone else. I'm sure there is a more elegant way to write the code, however this is the first time I've used MATLAB in 20 years :p Use at your own risk, I haven't double checked I'm getting the correct results yet (though will do before I use it for anything important).
edit, since writing this I've found that the output .txt file of temperatures is actually sensor temperatures which need to be corrected for emissivity and background temperature to obtain the target temperatures. (One way to do this is to use the software which comes free with the camera to create new output .csv files of temperatures and use those instead).
Thanks to bla who put me on the right track with dlmread.
M=dlmread('C:\18. Bats\20190321_064039\20190321_064039_temps.txt') % read in the text file as a matrix (call it M)
% note that file seems to be a list of temperature values for each pixel
% e.g. 1934 1935 1935 1960 2000 2199...
M = rot90( M , 1 ) % rotate M anti-clockwise by 1*90 (All the pictures were saved sideways for some reason so rotate for easier viewing)
a = min(M(:)); % find the minimum temperature in the image
b = max(M(:)); % find the maximum temperature in the image
imresize(M,1.64); % resize the image to fit the computer screen prior to showing it on the screen
imshow(M,[a b]); % show image on the screen and fit the colours so that white is the value with the highest temperature in the image (b) and black is the lowest (a).
h = drawpolygon('FaceAlpha',0); % Let the user draw a polygon around the region of interest (ROI)
%(this stops code until polygon is drawn)
maskOfROI = h.createMask(); % For each pixel in the image assign a binary number, pixels inside the polygon (ROI) area are given 1 outside are 0
selectedValues = M(maskOfROI); % Now get the image values for all pixels where the mask value is '1' (i.e. all pixels within the polygon) and call this selectedValues.
averageTemperature = mean(selectedValues); % Get the mean of selectedValues (i.e. mean of the temperatures inside the polygon area)
maxTemperature = max(selectedValues); % Get the max of selectedValues
minTemperature = min(selectedValues); % Get the min of selectedValues
I want to export matlab output to an excel file starting from G2 column and for this the code i had written is exporting the data correctly but not to the desired location .It is printing in 21st number of rows rather than 2nd.
the code is
ResultFile = xlsread('filename');
sz= size(ResultFile,1);
b= num2str(sz+1);
location = strcat('G2',b);
fprintf('value in location is %g\n',location);
xlswrite('filename',fnlarray,'Sheet1',location);
In the command
xlswrite(filename,A,sheet,xlRange)
you can either specify xlRange as a string defining the corners of the desired output region, or (provided that you have specified the sheet) only give the coordinates of the upper-left cell. If you want to write an array to a region "below and to the right of G2", this should be enough:
location = 'G2';
Concatenating 'G2' with the number of rows of the excel file + 1 does not really seem to make sense to me right now.
I am making location aware application. I have XML file on server containing information of different stores with latitude and longitude coordinates.
Now in my application i can get my current latitude and longitude coordinates and can parse XML file as well.
But how can i figure out nearest store according to my current coordinates from XML file?
If we use google Api it returns you xml file containing nearest locations according to query. but here in my case i am using xml file on server.
Please suggest
I think you'd be better off converting your data into a DB format (sqlite/mysql) so that the user can submit their lat/Lng point and just get the correct item returned...otherwise you'd need to parse and compare the whole file each time...but, you can still use that formula (it's really just shifting the comparison step to the DB query rather than within your app)
Edit: this has an example of a SQL query that implements haversine and returns x results: MySQL Great Circle Distance (Haversine formula)
This is the haversine formula for calculating distance between two points on the earth:
a = sin²(Δlat/2) + cos(lat1)*cos(lat2)*sin²(Δlong/2);
c = 2*atan2(√a, √(1−a));
d = R*c;
You can easily adapt it in obj-c.
Please note: R is radius of the earth = 6,371km;
So just calculate the latitude and the longitude difference of both points and calculate d based on it.
Hope this helps.