{"id":177231,"date":"2011-10-26T17:20:07","date_gmt":"2011-10-26T17:20:07","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/?post_type=blog&p=177231"},"modified":"2018-12-18T11:10:04","modified_gmt":"2018-12-18T19:10:04","slug":"overviews-and-pyramids-part-1-of-2-what-are-they-and-why-do-i-need-them","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/arcgis-desktop\/imagery\/overviews-and-pyramids-part-1-of-2-what-are-they-and-why-do-i-need-them","title":{"rendered":"Overviews and pyramids: Part 1 of 2, What are they and why do I need them?"},"author":4061,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[22931],"tags":[24651,25421,73231,23011],"industry":[],"product":[36991],"class_list":["post-177231","blog","type-blog","status-publish","format-standard","hentry","category-imagery","tag-image-analysis","tag-mosaic-dataset","tag-pyramids","tag-raster","product-arcgis-desktop"],"acf":{"short_description":"This is part 1 in a 2-part blog. Part 1 provides an overview of pyramids and overviews. Part 2 will provide you with some guidance on generating ","flexible_content":[{"acf_fc_layout":"content","content":"

This is part 1 in a 2-part blog. Part 1 provides an overview of pyramids and overviews. Part 2 will provide you with some guidance on generating them when creating a mosaic dataset.<\/em><\/i><\/p>\n

Basically\u2014overviews are not pyramids and pyramids are not overviews.\u00a0 But pyramids generated by ArcGIS have an .ovr extension (short for overview)\u2026Wait, did I just write that?<\/p>\n

Yes, the storage format for a pyramid is an .ovr file. But please don\u2019t confuse this with overviews. Fortunately, overviews are organized in a folder named *.overviews. Both are similar but pyramids are created for raster datasets and overviews are created for mosaic datasets.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n\n
<\/td>\n\n

Pyramids<\/h2>\n<\/td>\n

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Overviews<\/h2>\n<\/td>\n<\/tr>\n

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Description<\/h2>\n<\/td>\n

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Lower resolution (downsampled) images of the original data.<\/h2>\n<\/td>\n<\/tr>\n

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Purpose<\/h2>\n<\/td>\n

\n

Improve display speed and performance.<\/h2>\n<\/td>\n<\/tr>\n

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Created for<\/h2>\n<\/td>\n

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Raster datasets<\/h2>\n<\/td>\n

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Mosaic datasets<\/h2>\n<\/td>\n<\/tr>\n

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Format<\/h2>\n<\/td>\n

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Writes .ovr files\u2014with a few exceptions.<\/h2>\n<\/td>\n

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Writes as .tif files.<\/h2>\n<\/td>\n<\/tr>\n

\n

Reads pyramids stored externally as *.ovr or *.rrd or internally (e.g. MrSID)<\/h2>\n<\/td>\n<\/tr>\n

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Storage<\/h2>\n<\/td>\n

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In a single file that generally resides next to the source raster dataset and using the same name.<\/h2>\n<\/td>\n

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By default, in a folder next to the geodatabase with a *.overviews extension, or internally for ArcSDE.<\/h2>\n

Storage location is customizable.<\/h2>\n<\/td>\n<\/tr>\n

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Storage size<\/h2>\n<\/td>\n

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2\u00a0to 10% (compared to original raster datasets)<\/h2>\n<\/td>\n<\/tr>\n

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Downsampling factor<\/h2>\n<\/td>\n

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2<\/h2>\n<\/td>\n

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3 (default)<\/h2>\n<\/td>\n<\/tr>\n

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Extent<\/h2>\n<\/td>\n

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    \n
  • \n

    Each pyramid level covers the entire raster dataset.<\/h2>\n<\/li>\n
  • \n

    You can specify the number of levels to generate.<\/h2>\n<\/li>\n<\/ul>\n<\/td>\n

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    \n
  • \n

    Can cover part of or all of a mosaic dataset.<\/h2>\n<\/li>\n
  • \n

    Each level can consist of one or more images.<\/h2>\n<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n

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Options when building<\/h2>\n<\/td>\n

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    \n
  • \n

    Number of levels to create<\/h2>\n<\/li>\n
  • \n

    Resampling method<\/h2>\n<\/li>\n
  • \n

    Compression method & quality<\/h2>\n<\/li>\n<\/ul>\n<\/td>\n

\n