{"id":8338,"date":"2019-03-19T00:57:54","date_gmt":"2019-03-18T23:57:54","guid":{"rendered":"http:\/\/www.sigterritoires.fr\/?p=8338"},"modified":"2019-03-19T12:11:53","modified_gmt":"2019-03-19T11:11:53","slug":"how-to-use-landsat-images-free-with-qgis-2-8-for-ndvi","status":"publish","type":"post","link":"https:\/\/www.sigterritoires.fr\/index.php\/en\/how-to-use-landsat-images-free-with-qgis-2-8-for-ndvi\/","title":{"rendered":"How to use Landsat Images ( Free ) with QGis 2.8 for NDVI"},"content":{"rendered":"\n

In the previous two articles, we have discussed ( How\nto use Landsat images (free) with ArcGIS (ArcMap) for NDVI<\/a> , How\nto use Landsat images (free) with ArcGIS Pro for NDVI<\/a> ) the calculation and\ndisplay of NDVI with ArcMap and ArcGis Pro. In this article we will\ndiscuss how to achieve this\noperation\nwith QGis.
\nTo\ndownload Landsat images from Earth Explorer, check out\nthis\narticle: How\nto use Landsat Images ( Free ) in<\/a> your GIS<\/a> . <\/p>\n\n\n\n

Here we will use the raster calculator to calculate the NDVI<\/a>\n, then we will discuss how to create and use a specific colour\ngradient for this index.
\n \n\nIf you work with a Landsat 7 image,\nyou will load in QGis the bands 3 (red) and\n4 (infra-red). If you work\nwith a Landsat 8 image you will load the bands 4 (red)\nand 5 (infra-red).  \n\n\n\n<\/p>\n\n\n\n\n\n\n\n

\"\"<\/figure>\n\n\n\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nTo\nopen the raster calculator , click on the Raster-> Raster Calculator menu  \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

We will return the formula\n<\/p>\n\n\n\n

NDVI = PIR – R \/ PIR + R<\/strong> <\/p>\n\n\n\n

Where PIR<\/strong> is\nthe near infrared band and R<\/strong> is the red band<\/p>\n\n\n\n

In our example:\n
\n(\u00ab\u00a0LE72020272014184ASN00_B4\n@ 1\u00a0\u00bb – \u00ab\u00a0LE72020272014184ASN00_B3 @ 1\u00a0\u00bb) –\n(\u00ab\u00a0LE72020272014184ASN00_B4 @ 1\u00a0\u00bb + \u00ab\u00a0LE72020272014184ASN00_B3 @\n1\u00a0\u00bb) \n\nThe result displays as :  \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nYou can work\ndirectly\nusing this result but it is\nadvisable\nto refer to a standard symbology .\nWe\nare used to represent NDVI in a complete scale from -1 to +1\n( here the result expands from -0.5 to +0.506),\nto represent the negative values, which do not correspond to vegetation , by a\ngradient of blue, and the positive values , which correspond to vegetation , by\na gradient from green to red passing through the yellow . \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Only problem, this gradient\nis\nnot available in   QGis\nas such. <\/p>\n\n\n\n

To create it , open notepad and type the following text:\n
\n
\n<? xml version = \u00ab\u00a01.0\u00a0\u00bb encoding =\n\u00ab\u00a0UTF-8\u00a0\u00bb?><\/strong>
\n<svg<\/strong> xmlns<\/strong> =\n\u00ab\u00a0http:\/\/www.w3.org\/2000\/svg\u00a0\u00bb version = \u00ab\u00a01.1\u00a0\u00bb width =\n\u00ab\u00a0300px\u00a0\u00bb height = \u00ab\u00a045px\u00a0\u00bb<\/strong> viewBox<\/strong> = \u00ab\u00a00 0\n300 45\u00a0\u00bb><\/strong>
\n<g><\/strong>
\n<<\/strong> defs<\/strong> ><\/strong>
\n<<\/strong> linearGradient<\/strong> id = \u00ab\u00a0NDVI\u00a0\u00bb<\/strong>\ngradientUnits<\/strong> = \u00ab\u00a0<\/strong> objectBoundingBox<\/strong> \u00ab\u00a0<\/strong> spreadMethod<\/strong>\n= \u00ab\u00a0pad\u00a0\u00bb x1 = \u00ab\u00a00%\u00a0\u00bb x2 = \u00ab\u00a0100%\u00a0\u00bb y1 =\n\u00ab\u00a00%\u00a0\u00bb y2 = \u00ab\u00a00%\u00a0\u00bb><\/strong>
\n<stop offset = \u00ab\u00a00.00%\u00a0\u00bb stop-<\/strong> color<\/strong>\n= \u00ab\u00a0<\/strong> rgb<\/strong> (0,0,255)\u00a0\u00bb stop-opacity = \u00ab\u00a01.0000\u00a0\u00bb\n\/><\/strong>
\n<stop offset = \u00ab\u00a049.90%\u00a0\u00bb stop-<\/strong> color<\/strong>\n= \u00ab\u00a0<\/strong> rgb<\/strong> (190,210,255)\u00a0\u00bb stop-opacity =\n\u00ab\u00a01.0000\u00a0\u00bb \/><\/strong>
\n<stop offset = \u00ab\u00a050.00%\u00a0\u00bb stop-<\/strong> color<\/strong>\n= \u00ab\u00a0<\/strong> rgb<\/strong> (56,168,0)\u00a0\u00bb stop-opacity =\n\u00ab\u00a01.0000\u00a0\u00bb \/><\/strong>
\n<stop offset = \u00ab\u00a066.60%\u00a0\u00bb stop-<\/strong> color<\/strong>\n= \u00ab\u00a0<\/strong> rgb<\/strong> (255,255,0)\u00a0\u00bb stop-opacity =\n\u00ab\u00a01.0000\u00a0\u00bb \/><\/strong>
\n<stop offset = \u00ab\u00a0100.00%\u00a0\u00bb stop-<\/strong> color<\/strong>\n= \u00ab\u00a0<\/strong> rgb<\/strong> (255,0,0)\u00a0\u00bb stop-opacity = \u00ab\u00a01.0000\u00a0\u00bb\n\/><\/strong>
\n<\/<\/strong> linearGradient<\/strong> ><\/strong>\n
\n<\/<\/strong> defs<\/strong> ><\/strong>
\n<<\/strong> rect<\/strong> fill = \u00ab\u00a0<\/strong> url<\/strong> (#NDVI)\u00a0\u00bb\nx = \u00ab\u00a04\u00a0\u00bb y = \u00ab\u00a04\u00a0\u00bb width = \u00ab\u00a0292\u00a0\u00bb height =\n\u00ab\u00a037\u00a0\u00bb stroke = \u00ab\u00a0black\u00a0\u00bb stroke-width = \u00ab\u00a01\u00a0\u00bb \/><\/strong>\n
\n<\/ g><\/strong>
\n<metadata><\/strong>
\n<creator name = \u00ab\u00a0<\/strong> nasca<\/strong> \u00a0\u00bb\nversion = \u00ab\u00a01.0\u00a0\u00bb \/><\/strong>
\n<created date = \u00ab\u00a0Mon Mar 23 22:38:20 2015\u00a0\u00bb\n\/><\/strong>
\n<\/ metadata><\/strong>
\n<\/ svg><\/strong>
\n
\nRegister\nthis\nfile\nwith the name NDVI.svg<\/strong> in the \\ Program Files \\\nQGIS Wien \\ apps \\ qgis \\ resources \\<\/em> cpt<\/em> -City-qgis-min \\<\/em> cb<\/em>\n\\ div<\/em> <\/p>\n\n\n\n

Now we are going apply this gradient to the resulting raster of the NDVI calculation: Double click on the legend of the raster to open the Properties window
In the Style tab , change the rendering type<\/em> to \u00ab\u00a0Pseudo colour single band\u00a0\u00bb
Change the values from Min =-1 and from Max = 1. \u00a0\u00a0 <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

In the drop down \u00a0list of colour palette, go to \u00a0the last line and click New color palette<\/em><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

In the Color<\/em> Palette Type<\/em> , select\n-City<\/em> cpt<\/em> and\nclick\nOK<\/strong> \n\nThe palette cpt -City opens   \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Open \u00ab\u00a0Diverging\u00a0\u00bb<\/strong> item and select cb\/ div<\/strong> to find the ndvi palette that you have created .
Click on one of these, then click OK. Leave the default name and click OK
In Mode <\/strong>select equal intervals<\/em> .
In Class<\/strong> select , for example , 20<\/em> .
Click the Sort<\/strong> button
You will see the scale to be applied to the raster. \u00a0\u00a0 <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nClick\nOK<\/strong> to close the properties layer window and see the final result :\n \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

In the previous two articles, we have discussed ( How to use Landsat images (free) with ArcGIS (ArcMap) for NDVI , How to use Landsat images (free) with ArcGIS Pro for NDVI ) the calculation and…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"give_campaign_id":0,"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"sfsi_plus_gutenberg_text_before_share":"","sfsi_plus_gutenberg_show_text_before_share":"","sfsi_plus_gutenberg_icon_type":"","sfsi_plus_gutenberg_icon_alignemt":"","sfsi_plus_gutenburg_max_per_row":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[1260],"tags":[],"class_list":["post-8338","post","type-post","status-publish","format-standard","hentry","category-non-classe-en"],"aioseo_notices":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p6XU0A-2au","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts\/8338","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/comments?post=8338"}],"version-history":[{"count":0,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts\/8338\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/media?parent=8338"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/categories?post=8338"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/tags?post=8338"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}