{"id":2768,"date":"2025-06-18T18:31:06","date_gmt":"2025-06-18T18:31:06","guid":{"rendered":"https:\/\/3gsm.at\/?post_type=learning&#038;p=2768"},"modified":"2025-06-18T18:35:00","modified_gmt":"2025-06-18T18:35:00","slug":"essential-tips-for-using-ground-control-points-in-shapemetrix","status":"publish","type":"learning","link":"https:\/\/3gsm.at\/learning\/essential-tips-for-using-ground-control-points-in-shapemetrix\/","title":{"rendered":"Essential Tips for Using Ground Control Points in ShapeMetriX\u00a0"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\"><strong>Are You Placing GCPs Correctly?<\/strong>&nbsp;<\/h2>\n\n\n\n<p><em>Best Practices for GCP Placement:<\/em>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Distribute GCPs evenly throughout the survey area\u2014across both horizontal and vertical extents.&nbsp;<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Include multiple elevations, elevated features (e.g., berms, benches) and lower areas (e.g., pit floors), while placing GCPs to help fixing the model in 3D space more effectively.&nbsp;<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Use at least 3\u201310 well-distributed points, depending on the size of the area.&nbsp;<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ensure each GCP is clearly visible in multiple images from different angles (minimum 3\u20134 images).&nbsp;<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Mark GCPs clearly using checkerboards or contrasting targets so that they can be easily and precisely marked during processing&nbsp;<\/li>\n<\/ul>\n\n\n\n<p><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Aspect<\/strong>&nbsp;<\/td><td><strong>Good Practice<\/strong>&nbsp;<\/td><td><strong>Common Mistake<\/strong>&nbsp;<\/td><\/tr><tr><td>GCP Quantity&nbsp;<\/td><td>3\u201310+ spread across site&nbsp;<\/td><td>Too few GCPs&nbsp;<\/td><\/tr><tr><td>Vertical Placement&nbsp;<\/td><td>Include multiple elevations&nbsp;<\/td><td>Placing GCPs on similar elevations&nbsp;<\/td><\/tr><tr><td>Surveying&nbsp;<\/td><td>Use RTK\/PPK for high precision&nbsp;<\/td><td>Low-accuracy GPS or manual estimates&nbsp;<\/td><\/tr><tr><td>Image Coverage&nbsp;<\/td><td>GCP visible in 3\u20134+ images&nbsp;<\/td><td>Poor visibility \/ edge of images&nbsp;<\/td><\/tr><tr><td>Marking Accuracy&nbsp;<\/td><td>Zoom in and mark precisely&nbsp;<\/td><td>Rough or inconsistent marking&nbsp;<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<figure class=\"wp-block-image aligncenter size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"581\" src=\"https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-4-1024x581.png\" alt=\"\" class=\"wp-image-2769\" srcset=\"https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-4-1024x581.png 1024w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-4-300x170.png 300w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-4-768x436.png 768w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-4.png 1076w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><em>Fig 1. Example of a properly placed GCPs<\/em>&nbsp;<\/figcaption><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How GCPs used in ShapeMetriX Referencing Workflows?<\/strong>&nbsp;<\/h2>\n\n\n\n<p>In ShapeMetriX, GCPs are incorporated during the image alignment and scaling phase and their usage depends on the referencing workflow users choose.&nbsp;<\/p>\n\n\n\n<p><em>Referencing Workflow:<\/em>&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>After loading data and setting parameters, ShapeMetriX generates the full 3D model (coarse + dense reconstruction).&nbsp;<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>In the final step, externally surveyed GCPs are used to reference the model.&nbsp;\n<ul class=\"wp-block-list\">\n<li>The user marks GCPs in the images after reconstruction.<\/li>\n\n\n\n<li>ShapeMetriX performs a final geo-referencing step, aligning the model to the surveyed coordinates.\u00a0<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<p><\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-large\"><img decoding=\"async\" width=\"1024\" height=\"541\" src=\"https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-5-1024x541.png\" alt=\"\" class=\"wp-image-2770\" srcset=\"https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-5-1024x541.png 1024w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-5-300x158.png 300w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-5-768x406.png 768w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-5-1536x811.png 1536w, https:\/\/3gsm.at\/wp-content\/uploads\/2025\/06\/image-5.png 1600w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><em>Fig 2. Standard referencing using GCPs<\/em>&nbsp;<\/figcaption><\/figure>\n\n\n\n<p><em>Note<\/em>: The absolute accuracy of the final model is only as good as:&nbsp;<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The surveying accuracy of the GCP coordinates.&nbsp;<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The precision with which GCPs are marked in the images.<\/li>\n<\/ul>\n","protected":false},"featured_media":2771,"parent":0,"template":"","meta":{"_acf_changed":false},"class_list":["post-2768","learning","type-learning","status-publish","has-post-thumbnail","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/3gsm.at\/wp-json\/wp\/v2\/learning\/2768","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/3gsm.at\/wp-json\/wp\/v2\/learning"}],"about":[{"href":"https:\/\/3gsm.at\/wp-json\/wp\/v2\/types\/learning"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/3gsm.at\/wp-json\/wp\/v2\/media\/2771"}],"wp:attachment":[{"href":"https:\/\/3gsm.at\/wp-json\/wp\/v2\/media?parent=2768"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}