Hemadri Geospatial’s Post

💡 #Highcitedpaper #Universidad de Cádiz 🌊 Title: Comparison between the Employment of a Multibeam Echosounder on an Unmanned Surface Vehicle and Traditional #Photogrammetry as Techniques for Documentation and #Monitoring of Shallow-Water Cultural Heritage Sites: A Case Study in the #Bay of Algeciras 🔑 Keywords: #underwater cultural #heritage; #shallowwaters; #unmanned surface vehicles; #multibeam #echosounder; #photogrammetry 🔗 Link: https://lnkd.in/ghVZGabH 📜 Abstract：Over the last few years, due to various climatic, anthropogenic, and environmental factors, a large amount of submerged heritage has been unearthed and exposed to deterioration processes in the Bay of Algeciras. These impacts can be more severe in shallow waters, where the cultural heritage is more vulnerable to natural and human-induced impacts. This makes it urgent to document cultural heritage at risk of disappearing using different techniques whose efficiencies in the archaeological record need to be determined and compared. For this purpose, we have documented a shipwreck in the Bay of Algeciras using two techniques: photogrammetry and a multibeam echosounder. The photogrammetric method consists of obtaining a 3D model from numerous photographs taken of an object or a site. The processing software creates three-dimensional points from two-dimensional points found in the photographs that are equivalent to each other. Multibeam echosounders are capable of providing side scan imagery information in addition to generating contour maps and 3D perspectives of the surveyed area and can be installed in an unmanned surface vehicle. As a result, we have obtained two 3D visualisations of the shipwreck, i.e., digital copies, that are being used both for the analysis of its naval architecture and for its dissemination. Through the comparison of the two techniques, we have concluded that while a multibeam echosounder provides a detailed digital terrain model of the seabed, photogrammetry performed by divers gives the highest resolution data on objects and structures. In conclusion, our results demonstrate the benefits of this combined approach for accurately documenting and monitoring shipwrecks in shallow waters, providing valuable information for conservation and management efforts.

Some interesting discoveries on my first comparison of the recent (31 Jan 24) Geospatial Survey Specification from Historic England. Much of the requirement/guidance remains similar, though notably BIM has been removed from this version and in my view remains to be clearly defined. I do like that the guidance continues to press home the importance of repeatability and the necessity of permanent networks. I wish this was taken more seriously in general built environment works. What particularly caught my eye is that the maximum GSD (ground sampling distance) has been reduced significantly. I took a look at some of our larger scale flying projects like this one in Winchester: https://lnkd.in/eRgQmUVT This was flown with a common workhorse combination of the DJI M300 and P1 camera at around +60m above ground. 6 passes - double nadir and 4 oblique passes to provide elevation data. It maybe the obliques throwing the stats out but this averages 12mm GSD which would only make it suitable for 1:500 scale in the new guidance. Flying this configuration is an economical approach with mid cost range equipment and I have always thought provides a good base for topographic survey. Our traversed ground control showing it achieves +/-25mm. Be interested to know others thinking. One final comment and maybe I'll be accused of being too woke for this one. IMO its really time we stopped referring to UAVs as un-manned, you'd think in this day and age institutions would adopt the common term un-piloted in acknowledgement that pilots aren't only men. Detail matters as so much of the rest of the specification makes clear. #heritage #conservation #topographicsurvey #measuredsurvey #photogrammetry #estatesmanagement #architecture #engineering https://lnkd.in/dfCyqxtv

Historic Aerial Imagery Archives Now Available to All Public Sector Organisations For the first time, historic national aerial imagery is now freely accessible to all public sector organisations, providing critical support for a wide range of projects and future planning efforts. This initiative allows organisations to explore imagery archives dating back to 1999, offering a valuable glimpse into the past that can aid in understanding changes over time. With no cost to the public sector, this accessible data enables better resource management and more informed decision-making. This opportunity is part of the recently awarded APGB contract, which includes access to this imagery as one of its key components. Check out the full story on our website: https://lnkd.in/emwVWJyF #GeospatialData #AerialImagery #DigitalTransformation #UrbanPlanning #HistoricImagery #SmartCities

Excited to share this fantastic opportunity for public sector organisations to access historic aerial imagery for free! 🎉 Having this data available opens up so many possibilities for better planning, resource management, and understanding how our landscapes have changed over time. Proud to see how these tools can help drive smarter decision-making and innovation across various sectors. Let’s make the most of this valuable resource! #GeospatialData #PublicSectorInnovation #DigitalTransformation #MappingSolutions

#30DayMapChallenge | Day 27: Micromapping A look back at my Master's thesis characterizing tundra vegetation from traditional air photos and field measurements. I used a modern photogrammetry workflow and lidar-based classification to generate canopy heights, allowing small (some might even say micro) changes to be detected. Learn more here: https://lnkd.in/g56-JTDF #gis #cartography #datavisualization #geospatial #MakingMapsPretty #tundra #climatechange #photogrammetry #alaska #arcticgreening

Mapping the Mountains: photogrammetry, a survey technique pioneered in the second half of the 19th century, was particularly suited to mountainous terrain. Towards the end of the 19th century, trigonometrical surveys using conventional angle-measuring equipment, such as theodolites, were gradually being replaced by a technique known as photogrammetry, particularly suited to survey work in mountainous terrain. Instead of theodolites, surveyors used cameras attached to a tripod at fixed survey stations, for example on a summit, to take shots of surrounding peaks and intervening topographical features. Photographic data acquired in the field was processed back in the office and converted into maps. Larger areas could be surveyed more accurately using this method, leading to savings in time and money. It was a technique widely adopted by Canadian surveyors at the turn of the 20th century to open up the Canadian Rockies for tourism and the harnessing of natural resources. It was known there as ‘phototopography’. German and Austrian Alpine Clubs were also early converts and produced detailed maps of the Eastern Alps for the mountaineering fraternity using the method. Aerial photogrammetry supplanted terrestrial photogrammetry with the arrival of aviation. By the late 1940s, for example, Switzerland’s mapping agency had completely replaced terrestrial photographs with aerial images. Nowadays, aerial photography can also include satellite imagery. Mapping that is carried out from space is generally referred to as ‘remote sensing’. One significant spin-off from early photogrammetry projects is that the photographs (whose exact locations and dates are known) can tell us a lot about climate change and how mountain topography has evolved over time. For more info see: https://mountainlegacy.ca/ The story of photogrammetry will feature in ‘Mapping the Mountains’, a book on mountain cartography which I am currently writing for the Dutch Mountain Film Festival(DMFF.eu) and which is due to come out later this year. Image: Mount Robson (3,954m) – known as Yexyexéscen in the local language - in the Canadian Rockies photographed by A.O. (Arthur) Wheeler in 1911 as part of a topographic survey for the Canadian Alpine Club. #mappingthemountains                                                                      

The aerial photography and laser scanning data produced by the National Land Survey of Finland (NLS) saves several million euros for society each year. ✈️ Aerial photography and laser scanning data have a very large number of users in Finland. They are used, for example, to collect data on forest resources, maintain the Topographic Database, monitor agriculture, map flood events, and determine the level of property tax. 📍 In the FGI we have studied the use of laser scanning data to generate even more accurate data on forest resources. The result is the Forest database (Metsäkanta), which combines statistics with national laser scanning data and currently contains data on 5.8 billion individual trees. Covering more than 20 million hectares, it is one of the largest forest databases in the world. 🌲 Users of the Forest database can access data on individual trees, including the length and diameter, and estimate the value and carbon sequestration capacity of a forest area, for example. Read more 👉 https://lnkd.in/dtY-yE4x 📸 Drone laser scanning data from Evo, Hämeenlinna, produced for research purposes. The data enables forest analysis with individual tree-level accuracy. Photo by Antero Kukko. #remotesensing #laserscanning #digitaltwin

It generates precise, three-dimensional information about the shape of the Earth and its surface characteristics. How It Works: ✅ Laser Emission: A laser emits light pulses toward the ground. Reflection: The light pulses reflect off surfaces and return to the LiDAR sensor. ✅ Distance Calculation: The time taken for the pulses to return is measured, and the distance is calculated. Data Generation: These distance measurements create detailed, high-resolution 3D maps. Applications: ✅ Topography: Creating detailed maps of terrain. Forestry: Measuring tree heights and forest density. Urban Planning: Mapping city landscapes for infrastructure development. Archaeology: Revealing hidden structures beneath vegetation. #gis #GeospatialInnovation #mapping #map #gis #survey #cartography #surveyor #topography

"Understanding Geographic Data Vector Data: Stores data as coordinates and lines Precise and scalable Used for mapping boundaries, roads, and buildings Raster Data: Stores data as pixel grids Suitable for imagery and continuous data Used for aerial photography, elevation models, and climate data Knowing the difference between vector and raster data is crucial for effective Geographic Information Systems (GIS) analysis and mapping! #VectorData #RasterData #GIS #GeographicInformationSystems"

While most of our model validation is carried out by comparing the model results to direct current measurements, it's reassuring to see that our Oceanbox-tool also corresponds well to other data sources. 😄 Aerial photos from norgeibilder.no (top) and surface currents from the Oceanbox-tool (bottom) both indicate the presence of a large eddy in Vågsfjorden north of Harstad. #Oceanintelligence #Oceanography