{"id":32845,"date":"2019-04-11T14:47:13","date_gmt":"2019-04-11T14:47:13","guid":{"rendered":"http:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=32845"},"modified":"2019-04-11T16:58:42","modified_gmt":"2019-04-11T16:58:42","slug":"use-polar2grid-to-create-viirs-true-color-imagery-over-one-state-missouri","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/32845","title":{"rendered":"Use Polar2Grid to create VIIRS True Color imagery over one State (Missouri)"},"content":{"rendered":"
\"\"<\/a>

VIIRS True-Color Imagery over Missouri, 1942 UTC on 9 April 2019 (Click to enlarge)<\/strong><\/p><\/div>\n

Polar2Grid allows users to create true-color imagery from VIIRS (Visible Infrared Imaging Radiometer Suite) data from Suomi-NPP or NOAA-20. This tutorial will take you through the needed steps. Step one is to decide when you want the data; the ways to determine when a Polar Orbiter overflies a particular point are outlined in this blog post<\/a>, that points to this website<\/a>. For this blog post I’ve chosen Missouri. The image above shows a True-Color image over Missouri at about 19:42 UTC on 9 April 2019.<\/p>\n

To create true-color imagery, Polar2Grid requires VIIRS M-Bands 3, 4 and 5 (Blue (0.48 \u00b5m), Green (0.55 \u00b5m) and Red (0.67 \u00b5m), respectively, all with 750-m resolution); click here<\/a> for a list of all VIIRS bands). If the VIIRS I-Band 1 (at 0.64 \u00b5m) is present in the directory, then that image is used to sharpen the resultant image. Polar2Grid CREFL software also performs a simple atmospheric Rayleigh scattering removal; smoke and haze will still be apparent in the imagery, however.<\/p>\n

To create the imagery above, first order the data from NOAA Class. (Steps to follow are shown here<\/a>). Download the data into a unique directory. We are going to remap these data onto a map centered on Missouri, and for that to happen, Polar2Grid needs mapping parameters. These can be generated automatically with the p2_grid_helper.sh script that comes with Polar2Grid software. From the bin directory, I entered this command to put the grid parameters in a file .<\/p>\n

\/p2g_grid_helper.sh missouri -93.0 38.0 500 -500 2000 2000 > my_grids.txt<\/p><\/blockquote>\n

The line of data entered into that file is this:<\/p>\n

missouri, proj4, +proj=lcc +datum=WGS84 +ellps=WGS84 +lat_0=38.000 +lat_1=38.000 +lon_0=-93.000 +units=m +no_defs, 2000, 2000, 500.000, -500.000, -99.055deg, 42.352deg<\/p><\/blockquote>\n

Now I’m ready to generate a true-color image (corrected ceflectance — crefl — imagery) with Polar2Grid, using this command:<\/p>\n

.\/polar2grid.sh crefl gtiff –grid-configs \/home\/scottl\/Polar2Grid\/polar2grid_v_2_2_1\/bin\/my_grids.txt -g missouri -f \/data-hdd\/storage\/Polar2GridData\/09April\/<\/p><\/blockquote>\n

The flags “–grid-configs <path to directory where file created by p2g_grid_help sits” and “-g map <name of map inside that file>” instruct to the Polar2Grid software to pull the mapping data for the defined grid out of the file. Otherwise, the data are in satellite projection. This polar2grid.sh invokation created a file named ‘j01_viirs_true_color_20190409_194226_missouri.tif’; I want to put a map on it so it is easier to georeference, and that is done using this shell in the Polar2Grid bin directory:<\/p>\n

.\/add_coastlines.sh –add-borders –borders-resolution=f –borders-level=2 –borders-outline=’black’ j01_viirs_true_color_20190409_194226_missouri.tif<\/p><\/blockquote>\n

This adds a map to the image, then converts it to the png file (j01_viirs_true_color_20190409_194226_missouri.png) that is shown above.<\/p>\n

After doing the same steps for a series of clear days in the midwest (09 March 2019<\/a>, 15 March 2019<\/a>, 21 March 2019<\/a>, 26 March 2019<\/a>, 31 March 2019<\/a>), and annotating and concatenating the images in an animation, the greening up of Spring is apparent. See below.<\/p>\n

\"\"<\/a>

NOAA-20 VIIRS True Color Imagery on select mostly clear days over the mid-Mississippi Valley, dates and times as indicated in the image (Click to enlarge)<\/p><\/div>\n

Special shout-out to Dave Hoese, SSEC\/CIMSS, for crafting software that is so easy to use to produce excellent satellite imagery.<\/p>\n","protected":false},"excerpt":{"rendered":"

Polar2Grid allows users to create true-color imagery from VIIRS (Visible Infrared Imaging Radiometer Suite) data from Suomi-NPP or NOAA-20. This tutorial will take you through the needed steps. Step one is to decide when you want the data; the ways to determine when a Polar Orbiter overflies a particular point are outlined in this blog […]<\/p>\n","protected":false},"author":19,"featured_media":32861,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[78,39,48],"tags":[],"class_list":["post-32845","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-noaa-20","category-training","category-viirs"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/32845","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/users\/19"}],"replies":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/comments?post=32845"}],"version-history":[{"count":12,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/32845\/revisions"}],"predecessor-version":[{"id":32866,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/32845\/revisions\/32866"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media\/32861"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=32845"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=32845"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=32845"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}