Latest Contributions by SantiagoTrujillo

‎08-24-2012

I have the same problem with black or green areas and rectified rasters. It seems to occur more when I have to rotate the raster being georeferenced. Yes, I can reset the band values to zero to make them transparent, but I'd like to permanently set them to nodata so I don't have to adjust the image each time I bring the raster into a map. Suggestions? Hi, Try using the Setnull function that can be found in Map algebra, I havn't used this one myself but it seems to be crated for that purpose. You can also try using this document as a guide http://ibis.colostate.edu/WebContent/WS/ColoradoView/TutorialsDownloads/CO_RS_Tutorial2.pdf for another type of process. Hope it works for you.

‎08-21-2012

Generally speaking, the RPC or rational polynomial coefficients are created by the sensor, usually a satellite. In most cases, the RPCs are included with satellite imagery, as mentioned here. In terms of ortho rectifying your UAV data, then if the RPCs were not generated in the process then you must find a way to create check points based on surveyed ground control points that should have ideally been collected prior to flying the project. There are other software packages that can help you orthorectify with manually added checkpoints, like ENVI. Yeah I was beginning to think I would have to use another software to orthorectify my images. I saw some ENVI tutorial and they did show how to do it manually, but still there must be some way to create this RPC's from the information the UAV gives me (altitude, lat and long) and the information of the camera. If someone has information on how to create RPC's from your own aerial photographs it would be really helpful. Anyway thanks for your help I'll give it a try using ENVI and if it works then maybe there'll be no need to create RPC's to be read on ArcGIS.

‎08-20-2012

HI, I use a UAV to take some aerial images, but I want to use this images to be able to measure true distances and for that purpose I have to orthorectify them. I looked in the the help menu in ArcGIS and it says that what I need are the RPC's (rational polynomial coefficients) and a DEM, also some control points would help make an accurate orthophoto. What I need help with is creating this RPC's, because I have no idea what they are and they seem to be the key to all of this. Can anyone out there help me by telling me what RPC's are, and how to create them in a proper way that ArcGIS identifies it as part of the raster image I upload. Thanks,

‎08-01-2012

If you know your constants, can't you just use the raster calculator? Hmmmmm I'll try to do it using the raster calculator and see what I get. As I said before, I'm relatively new to ArcGIS so I don't know many tools to do what I want. Thanks a lot for your answer, I'll reply after I give it a try.

‎08-01-2012

Hi, I have several LandSAT 5 Images including the midinfrared ones that correspond to the Band 6 raster data. As my graduation project I have to estimate the temperature that each pixel (which go from 0-255) represents. So long I've found the equation that will allow me to estimate the temperature, but I'm relatively new to ArcGIS and don't know of any tools or functions that will allow me to assign temperature values to the cells, depending on the values they already have. There are two equations to get temperature values form this LandSAt images. These are as follows: Equation 1. Obtaining Radiance Lλ = ((LMAXλ - LMINλ)/(QCALMAX-QCALMIN)) * (QCAL-QCALMIN) + LMINλ where: Lλ = Spectral Radiance at the sensor's aperture in watts/(meter squared * ster * µm) Grescale = Rescaled gain (the data product "gain" contained in the Level 1 product header or ancillary data record) in watts/(meter squared * ster * µm)/DN Brescale = Rescaled bias (the data product "offset" contained in the Level 1 product header or ancillary data record ) in watts/(meter squared * ster * µm) QCAL = the quantized calibrated pixel value in DN LMINλ= the spectral radiance that is scaled to QCALMIN in watts/(meter squared * ster * µm) LMAXλ = the spectral radiance that is scaled to QCALMAX in watts/(meter squared * ster * µm) QCALMIN = the minimum quantized calibrated pixel value (corresponding to LMINλ) in DN = 1 for LPGS products = 1 for NLAPS products processed after 4/4/2004 = 0 for NLAPS products processed before 4/5/2004 QCALMAX = the maximum quantized calibrated pixel value (corresponding to LMAXλ) in DN = 255 Equation 2. Obtaning Temperature y Kelvin T= K2/(ln*(K1/Lλ+1) ) Where: T = Effective at-satellite temperature in Kelvin K2 = Calibration constant 2 from Table 11.5 K1 = Calibration constant 1 from Table 11.5 L = Spectral radiance in watts/(meter squared * ster * µm) I alerady know all the constants, but I wouldn't know how to apply this to my image so that the pixels represent temeprature instead of just a value from 0-255. Thanks for anyone who can help me out with this.

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Latest Contributions by SantiagoTrujillo

Re: Georeferencing Aerial Photographs and pixel orientation

Re: Orthorectifying Aerial Photographs

Orthorectifying Aerial Photographs

Re: How to estimate the temperature of a LandSAT Image based on the Band 6 raster dat

How to estimate the temperature of a LandSAT Image based on the Band 6 raster data?

Orthorectifying Aerial Photographs

Re: Orthorectifying Aerial Photographs