TEORETIČNA GOSTOTA LIDARSKIH TOČK ZA TOPOGRAFSKO KARTIRANJE V NAJVEČJIH MERILIH

Mihaela Triglav Čekada, Fabio Crosilla, Mojca Kosmatin Fras

DOI: 10.15292/geodetski-vestnik.2010.03.389-402

 

THEORETICAL LIDAR POINT DENSITY FOR TOPOGRAPHIC MAPPING IN THE LARGEST SCALES

Mihaela Triglav Čekada, Fabio Crosilla, Mojca Kosmatin Fras

DOI: 10.15292/geodetski-vestnik.2010.03.403-416

 

Izvleček:

Gostota lidarskih točk na površinsko enoto je pomemben podatek pri naročanju lidarskih podatkov, ki odločilno vpliva tudi na ceno lidarskega snemanja. V članku najprej obravnavamo teoretični izračun minimalne gostote lidarskih točk, ki je potrebna za zajem topografskih podatkov v največjih merilih. Za ta namen smo uporabili teorem vzorčenja. Ker pa so topografski objekti in pojavi, ki so predstavljeni na topografskih kartah in v topografskih bazah, velikokrat pod vegetacijo (ceste, vodna telesa itd.), moramo poznati tudi delež prodiranja laserskih žarkov skozi vegetacijo za območje, kjer bomo zajemali topografske podatke. V raziskavi smo na testnem primeru na območju mesta Nova Gorica izračunali delež prodiranja laserskih žarkov za štiri različne vegetacijske tipe: redko mediteransko vegetacijo, gost termofilen listnati gozd, mešano vegetacijo (travniki, sadovnjaki in gozd) in pozidano območje. S povezavo teoretične minimalne gostote lidarskih točk in deleža prodiranja smo določili minimalno gostoto lidarskih točk za potrebe zajema podatkov na topografskih kartah največjih meril oziroma v topografskih bazah primerljive podrobnosti (od 1 : 1000 do 1 : 10.000).

Ključne besede: zračno lasersko skeniranje, lidar, topografija, gostota lidarskih točk, teorem vzorčenja

 

Abstract:

When ordering LiDAR data, LiDAR point density per surface unit is important information with decisive influence on the price of the LiDAR survey. The paper first deals with the theoretical calculation of the minimum LiDAR point density, necessary for the acquisition of topographic data of the largest scales. For this purpose the sampling theorem is used. However, since topographic objects (roads, water bodies, etc.) and phenomena represented on topographic maps and in topographic bases are in many cases located under vegetation, also the rate of laser beam penetration through vegetation for the area where the topographic data are to be gathered has to be known. In a research on a test case conducted in the area of the town Nova Gorica we calculated the rate of laser beam penetration for four different vegetation types: scarce Mediterranean vegetation, thick thermophilic deciduous forest, mixed vegetation (meadows, orchards and forest) and built-up area. By connecting the theoretic minimum LiDAR point density with the rate of penetration, we defined the minimum LiDAR point density for the needs of data acquisition on topographic maps of the largest scales or in topographic bases of comparable detail (from 1 : 1000 to 1 : 10,000).

Keywords: airborne laser scanning, LiDAR, topography, LiDAR point density, sampling theorem

 

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