<liclass="toctree-l4"><aclass="reference internal"href="../installation/#step-1-check-virtualization-support">Krok 1. Zkontrolujte podporu virtualizace</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../installation/#step-2-install-requirements">Krok 2. Požadavky na instalaci</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../installation/#step-3-check-memory-and-cpu-allocation">Krok 3. Zkontrolujte přidělení paměti a procesoru</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../installation/#step-4-download-webodm">Krok 4. Stáhněte si WebODM</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../installation/#step-2-check-additional-requirements">Krok 2. Zkontrolujte další požadavky</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../installation/#step-3-download-and-launch-webodm">Krok 3. Stažení a spuštění WebODM</a></li>
</ul>
</li>
</ul>
</li>
<liclass="toctree-l2"><aclass="reference internal"href="../installation/#basic-commands-and-troubleshooting">Základní příkazy a řešení potíží</a></li>
<liclass="toctree-l2"><aclass="reference internal"href="../installation/#hello-webodm">Dobrý den, WebODM!</a><ul>
<liclass="toctree-l3"><aclass="reference internal"href="../installation/#running-on-more-than-one-machine">Spuštění na více než jednom počítači</a></li>
<liclass="toctree-l2"><aclass="reference internal"href="../tutorials/#creating-high-quality-orthophotos">Vytváření vysoce kvalitních ortofotomap</a></li>
<liclass="toctree-l2"><aclass="reference internal"href="../tutorials/#using-docker">Použití aplikace Docker</a><ul>
<liclass="toctree-l3"><aclass="reference internal"href="../tutorials/#listing-docker-machines">Výpis strojů Docker</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../tutorials/#accessing-logs-on-the-instance">Přístup k protokolům instance</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../tutorials/#command-line-access-to-instances">Přístup k instancím z příkazového řádku</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../tutorials/#cleaning-up-after-docker">Úklid po Dockeru</a></li>
<liclass="toctree-l2"><aclass="reference internal"href="../tutorials/#using-odm-from-low-bandwidth-location">Použití ODM z místa s nízkou šířkou pásma</a><ul>
<liclass="toctree-l3"><aclass="reference internal"href="../tutorials/#what-is-this-and-who-is-it-for">Co to je a pro koho je to určeno?</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../tutorials/#prep-data-and-project">Příprava dat a projektu</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../tutorials/#resize-droplet-pull-pin-run-away">Resize droplet, pull pin, run away</a></li>
<liclass="toctree-l4"><aclass="reference internal"href="../tutorials/#after-it-finishes-assuming-you-survive-that-long">Po jeho skončení (za předpokladu, že přežijete tak dlouho)</a></li>
</ul>
</li>
</ul>
</li>
<liclass="toctree-l2"><aclass="reference internal"href="../tutorials/#using-potree-3d-viewer-module-on-webodm">Použití modulu Potree 3D viewer na WebODM</a><ul>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/auto-boundary/#what-is-auto-boundary">Co je automatická hranice?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/auto-boundary/#when-is-auto-boundary-helpful">Kdy je automatická hranice užitečná?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/auto-boundary/#why-would-one-use-auto-boundary">Proč by měl někdo používat automatické ohraničení?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/boundary/#what-is-boundary-geojson">Co je to Hranice [GeoJSON]?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/boundary/#when-is-boundary-geojson-appropriate">Kdy je vhodné použít Hranice [GeoJSON]?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/boundary/#why-would-one-use-boundary-geojson">Proč by měl někdo použít Hranice [GeoJSON]?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/boundary/#how-would-one-create-boundary-geojson">Jak se vytváří Hranice [GeoJSON]?</a><ul>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/build-overviews/#what-are-overviews">What Are Overviews?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/build-overviews/#when-are-overviews-appropriate">When are Overviews appropriate?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/build-overviews/#why-would-one-use-overviews">Why would one use Overviews?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/camera-lens/#what-are-camera-lens-models">Co jsou modely objektivů fotoaparátů?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/camera-lens/#when-are-manual-selections-appropriate">Kdy je vhodný ruční výběr?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../arguments/camera-lens/#why-would-one-use-a-particular-camera-lens-model">Proč používat určitý model objektivu fotoaparátu?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../large/#getting-started-with-distributed-split-merge">Getting Started with Distributed Split-Merge</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../large/#understanding-the-cluster">Understanding the Cluster</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../large/#accessing-the-logs">Accessing the Logs</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../faq/#can-i-process-two-or-more-orthophoto-geotiffs-to-stitch-them-together">Mohu zpracovat dva nebo více ortofotografických souborů GeoTIFF a spojit je dohromady?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../faq/#the-software-is-not-using-all-of-my-cpu-cores-memory-gpu-all-of-the-times-is-it-normal">The software is not using all of my CPU cores / memory / GPU all of the times. Is it normal?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../faq/#if-i-use-the-native-version-of-the-software-how-can-i-allocate-more-resources-for-processing">If I use the native version of the software, how can I allocate more resources for processing?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../faq/#i-want-to-build-a-commercial-application-that-includes-odm-do-i-need-a-commercial-license">Chci vytvořit komerční aplikaci, která zahrnuje ODM. Potřebuji komerční licenci?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../faq/#are-there-other-licensing-options-aside-from-the-agplv3">Existují kromě licence AGPLv3 i jiné možnosti licencování?</a></li>
<liclass="toctree-l3"><aclass="reference internal"href="../faq/#your-computer-is-running-out-of-memory-what-can-you-do">Your computer is running out of memory, what can you do?</a></li>
<h1>Map accuracy<aclass="headerlink"href="#map-accuracy"title="Permalink to this heading"></a></h1>
<p>Accuracy can be defined as the degree or closeness to which the information on a map matches the values in the real world. Therefore, when we refer to accuracy, we are talking about quality of data and about number of errors contained in a certain dataset (Pascual 2011).</p>
<p><strong>Relative or Local accuracy</strong></p>
<p>Local or relative accuracy can be defined as the degree to which de distances between two points on a map correspond to the actually distances between those points in the real world.</p>
<p>Relative accuracy is independent of the location of the map in the world, so a map can have a high relative accuracy (in size and shape) but its position in the world can be shifted (Figure 1).</p>
<figureclass="align-center">
<imgalt="Model showing high relative accuracy"src="../_images/rel_accuracy.png"/>
</figure>
<p><em>Figure 1. Model showing high relative accuracy but misplaced according to its real world position</em></p>
<p><strong>Absolute or global Accuracy</strong></p>
<p>Absolute accuracy is the accuracy of the reconstruction in relation to its true position on the planet (Pix4D 2019). Figure 2 shows a relative and absolute accurate model, as the points are correctly placed according to its real world position.</p>
<figureclass="align-center">
<imgalt="Model showing high absolute accuracy"src="../_images/abs_accuracy.png"/>
</figure>
<p><em>Figure 2. Model showing high relative and absolute accuracy. Placed correctly according to its real world position</em></p>
<p><strong>An Accuracy level for each project</strong></p>
<p>Each project has specific accuracy needs to be met. For instance assessing the progress in a construction site or measuring an area affected by a fire does not require the use of GCP, since absolute accuracy will not impact the decision making process. In the other hand, there are tasks on which accuracy is critical, for example project compliance evaluations and land title surveying, which require a higher relative and absolute accuracy.</p>
<sectionid="what-to-expect">
<h2>What to expect<aclass="headerlink"href="#what-to-expect"title="Permalink to this heading"></a></h2>
<p>In general terms, one can expect the relative accuracy to be in the order of 1 to 3 times the average GSD for the dataset. And as for the absolute accuracy, one must consider that it is dependent of the GPS unit mounted in the UAV but the horizontal accuracy of a standard GPS is usually in the range of 2 to 6 meters and the vertical accuracy between 3 to 4 times the horizontal accuracy.</p>
<p>When using GCP, absolute accuracy can be improved to 2.5 times GSD for the horizontal accuracy and 4 times the GSD for the vertical accuracy (Madawalagama 2016).</p>
<p>At a GSD of 1cm, the accuracy is to that of the RTK GNSS, and is within 1:200 scales according to NSDI & FGDC mapping accuracy standards during sub-optimal conditions (Barry 2013).</p>
<sectionid="aspects-impacting-map-accuracy">
<h3>Aspects impacting map accuracy<aclass="headerlink"href="#aspects-impacting-map-accuracy"title="Permalink to this heading"></a></h3>
<p><strong>Weather</strong></p>
<p>Weather conditions have direct impact in the photogrammetry results, so it is important to consider cloud coverage, wind speed, humidity, sun’s altitude and other factors influencing the UAV stability and terrain illumination.</p>
<p><strong>Cameras</strong></p>
<p>Bigger and better sensors produce less noise and more clearly focused images. Also consider that rolling shutter cameras produce distorted images when the UAV is moving, so global or mechanical shutter cameras are advised for mapping jobs.</p>
<p><strong>Flight altitude</strong></p>
<p>The higher the flight altitude, the larger the image footprint and GSD. The resulting larger GSD the accuracy will be decreased as there will be less detail in the recognizable features. When a smaller GSD is required an altitude of 3 to 4 times the height of the highest point is recommended.</p>
<p><strong>Flight speed</strong></p>
<p>Flight speed have special effect in cameras equipped with rolling shutter, while those equipped with global or mechanical shutter tends to reduce this effect. UAV equipped with RTK positioning systems are also affected with the speed, but with hover at each photo taken, you can get very good accuracy. If instead you are moving during each photo take, the accuracy is going to be limited by two factors: the speed at which you are moving multiplied by the 1 second increments of RTK (Mather 2020).</p>
</section>
</section>
<sectionid="references">
<h2>References<aclass="headerlink"href="#references"title="Permalink to this heading"></a></h2>
<p>Barry, P., & Coakley, R. «Accuracy of UAV photogrammetry compared with Network RTK GPS.» Baseline Surveys. 2013. <aclass="reference external"href="http://uav.ie/PDF/Accuracy_UAV_compare_RTK_GPS.pdf">http://uav.ie/PDF/Accuracy_UAV_compare_RTK_GPS.pdf</a> (accessed 10 13, 2020).</p>
<p>Drone Deploy. How Do I Use Ground Control Points?: A guide to using ground control points with drone mapping software. 5 8, 2017. <aclass="reference external"href="https://www.dronedeploy.com/blog/what-are-ground-control-points-gcps/">https://www.dronedeploy.com/blog/what-are-ground-control-points-gcps/</a> (accessed 7 9, 2020).</p>
<p>Madawalagama, S.L., Munasinghe, N., Dampegama, S.D.P.J. and Samarakoon, L. «Low-cost aerial mapping with consumer grade.» 37th Asian Conference on Remote Sensing. Colombo, Sri Lanka, 2016.</p>
<p>Mather, Stephen. OpenDroneMap. 30 de Marzo de 2020. <aclass="reference external"href="https://community.opendronemap.org/t/the-accuracy-of-webodm-using-rtk-uavs/3937">https://community.opendronemap.org/t/the-accuracy-of-webodm-using-rtk-uavs/3937</a> (accessed 10 12, 2020).</p>
<p>Pascual, Manuel S. GIS Lounge: GIS Data: A Look at Accuracy, Precision, and Types of Errors. 11 6, 2011. <aclass="reference external"href="https://www.gislounge.com/gis-data-a-look-at-accuracy-precision-and-types-of-errors/">https://www.gislounge.com/gis-data-a-look-at-accuracy-precision-and-types-of-errors/</a> (accessed 07 09, 2020).</p>
<p>Pix4D. «What is accuracy in an aerial mapping project?» Pix4D. 25 de 05 de 2019. <aclass="reference external"href="https://www.pix4d.com/blog/accuracy-aerial-mapping">https://www.pix4d.com/blog/accuracy-aerial-mapping</a> (accessed 10 13, 2020).</p>
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