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More than 10 years have passed since the coining of the term volunteered geographic information (VGI) in 2007. A recently published article presents the results of a review of the literature concerning VGI.
A total of 346 articles published in 24 international refereed journals in GIScience between 2007 and 2017 have been reviewed. The review has uncovered varying levels of popularity of VGI research over space and time, and varying interests in various sources of VGI (e.g. OpenStreetMap) and VGI-related terms (e.g. user-generated content) that point to the multi-perspective nature of VGI.

Content-wise, using latent Dirichlet allocation (LDA), this study has extracted 50 specific research topics pertinent to VGI. The 50 topics have been subsequently clustered into 13 intermediate topics and three overarching themes to allow a hierarchical topic review. The overarching VGI research themes include

(1) VGI contributions and contributors,

(2) main fields applying VGI, and

(3) conceptions and envisions.

The review of the articles under the three themes has revealed the progress and the points that demand attention regarding the individual topics. This article also discusses the areas that the existing research has not yet adequately explored and proposes an agenda for potential future research endeavors.

Several main points for further research discussed in the review include the strengthening of VGI quality assurance, streamlined large-scale, multiple-source, and multiple-purpose VGI handling and integration, VGI contributor studies, privacy protection, tools and methods for geospatial big data processing and analysis, applied VGI studies, sustainability of VGI applications, conceptual and theoretical underpinnings, and user empowerment.

Yan, Y., C. Feng, W. Huang, H. Fan, Y. Wang & A. Zipf (2020) Volunteered geographic information research in the first decade: a narrative review of selected journal articles in GIScience, International Journal of Geographical Information Science, DOI: 10.1080/13658816.2020.1730848

On Tuesday, 25.02.2020, the 3DGeo group and the SYSSIFOSS project partner from KIT organised a collaborative data processing event. 24 participants spent 6 hours (10:00-16:00) extracting individual trees from airborne LiDAR forest point clouds.

Participants at work in the virtual forest

Participants at work in the virtual forest

In the SYSSIFOSS project, the segmented 3D tree models are required to simulate 3D forest stands when combined with a forest growth simulator (find further information about the project below). Tree extraction from airborne LiDAR data is a very time-expensive task, which is also a lot more fun when many people are working on it together.

During the mapathon the number of extracted trees was projected to the screen in the front and kept everyone motivated. Tasty food and drinks were provided by the organisers and after reaching the 200-tree mark, the music started playing, which contributed to a great atmosphere. Since it was the last day of carnival, 3DGeo members also dressed in costumes. Even though extracting trees was tricky at times as we were struggling to see the wood for the trees, we had a lot of fun…

…and in the end we were happy to end the day with exactly 333 trees segmented.

In the end, 333 trees were segmented

In the end, 333 trees were segmented

Segmented trees

Segmented trees

Thanks again to all participants!

About SYSSIFOSS

In SYSSIFOSS we are using 3D LiDAR forest data to create a database of diverse model trees (different species and characteristics). Using tree positions and parameters provided by a forest growth simulator, 3D forest scenes will be assembled from these model trees. They serve as input for the Heidelberg LiDAR Operations Simulator (HELIOS). Based on the resulting simulations, we will conduct a sensitivity analysis to identify the most important factors (field inventory design, field plot size, statistical model, LiDAR acquisition settings, etc.) influencing LiDAR based forest inventories. Furthermore, we will investigate the potential of synthetic data to minimize the amount of field data collection.

Schäfer, J., Faßnacht, F., Höfle, B. & Weiser, H.(2019): Das SYSSIFOSS-Projekt: Synthetische 3D-Fernerkundungsdaten für verbesserte Waldinventurmodelle. In: 2. Symposium zur angewandten Satellitenerdbeoachtung, Cologne, Germany, pp.1-1.

Find further details about the SYSSIFOSS project on the project website, in recent blogposts, or on Twitter (#SYSSIFOSS).

SYSSIFOSS is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - project number: 411263134.

The last days of field work in Erg Chebbi continued at the star dune to wrap up final tasks: filling gaps in the data, adding some dune arms to the ground penetrating radar data, … All data acquisition at the star dune was concluded successfully, although the group was off to a late start. The car that tranports the equipment near the dune field got a few meters too close into the sand, and had to be dug and pushed out in a joint effort.

Digging the institute's car out of sand

Digging the institute's car out of sand

On the positive side, this was a good training for the final day of field work at Erg Ziz, a newly explored dune field North-West of Hassilabied. In addition to ERT and GPR profiles, a 1.8 m whole was dug to expose a ground profile. The profile was discusses on site and samples taken from the eleven identified layers for lab analysis back in Heidelberg. The stratification showed alternating layers of aeolian deposits, playa, and included visible influences of water-driven processes.

Ground profile in playa

Ground profile in playa

Laying out an ERT over the playa

Laying out an ERT over the playa

Ground penetrating radar along ERT profile

Ground penetrating radar along ERT profile

Borehole drilling between dune arms

Borehole drilling between dune arms

For the remainder, the group will sort out samples and clean the equipment, so that everything is in order for the journey back. On Thursday, it’s time to say goodbye to the beautiful Erg Chebbi region once again. We are very happy to take so much cool data with us, which will help to find out more about the history of the desert!

This was it from this year’s field course in Erg Chebbi, Morocco. Catch up on all blog posts here and check out our tweets under #HeidelErg.

After three days of hard work in the field, Sunday was halftime workshop at HeidelErg. with diverse topics all around dunes, with and beyond the data collected in ErgChebbi.

Manuel Herzog introduced the first results from the geophysical measurements with regards to dune stratification. Ground penetrating radar in combination with Electrical Resistivity Tomography already shows promising results. The full analysis requires topographical correction, which relies on GNSS measurements of the transects. Katharina Anders presented the first version of the 3D model of the star dunes in connection with repeat GNSS measurements of the dunes crests. Master student Karl Wutzer showed possibilities to discriminate dune sands based on shape, color and especially grain size, for which he develops a new approach using image analysis.

Moreover, two researchers who joined the field course, presented their work to the group. Mateusz Kryger (University of Cologne) presented his work on numerical modeling of dunes. This stimulated a discussion about uni- or bi-modal wind directions in order to understand the formation of specific dune forms, such as barchans and longitudinal seif dunes.

Merve Seçkin-Kryger (German Aerospace Center) gave insight into her experiments in a laboratory wind tunnel, where she uses coated hollow microspheres to build up cm-size barchan dunes. These experiments help to understand dune forms we observe on Earth as well as on other planets, e.g. Mars.

Presenting results of geophysical measurements

Presenting results of geophysical measurements

Numerical modeling of dunes

Numerical modeling of dunes

Dune formation via wind tunnel experiments

Dune formation via wind tunnel experiments

Grain-based "crime scene" investigation using image analysis methods

Grain-based"crime scene" investigation

Location-based games have become popular in recent years, with Pokémon Go and Ingress being two very prominent examples. Some location-based games, known as Serious Games, go beyond entertainment and serve additional purposes such as data collection. Such games are also found in the OpenStreetMap context and playfully enrich the project’s geodatabase. Examples include Kort and StreetComplete. This article examines the role of spatially structured scoring systems as a motivational element. It is analysed how spatial structure in scoring systems is correlated with changes observed in the game behaviour. For this purpose, our study included two groups of subjects who played a modified game based on StreetComplete in a real urban environment. One group played the game with a spatially structured scoring system and the other with a spatially random scoring system. We evaluated different indicators and analysed the players’ GPS trajectories. In addition, the players filled out questionnaires to investigate whether they had become aware of the scoring system they were playing. The results obtained show that players who are confronted with a spatially structured scoring system are more likely to be in areas with high scores, have a longer playing time, walk longer distances and are more willing to take detours. Furthermore, discrepancies between the perception of a possible system in the scoring system and corresponding actions were revealed. The results are informative for game design, but also for a better understanding of how players interact with their geographical context during location-based games.

Find all details in the full paper:

Westerholt, R., Lorei, H. & Höfle, B. (2020): Behavioural Effects of Spatially Structured Scoring Systems in Location-Based Serious Games - A Case Study in the Context of OpenStreetMap. In: ISPRS Int. J. Geo-Inf. Vol 9 (2), pp. 1-27. DOI: https://doi.org/10.3390/ijgi9020129.

During the first three days of the field course in Erg Chebi, data collection focussed on the star dune with groups of students applying different techniques of geophysical and topographic surveying. Today, data was checked to plan the remaining three field days. A recap of this intermediate data revision will follow. For today, we’d like to reflect this year’s field course in numbers:

300 m of Electrical Resistivity Tomography transects were laid out across several arms of the dune field; 13 m of boreholes were drilled between the dune arms; 60 km were walked (by the same person!) along and across Erg Chebbi, and thereby 20 kg of sand were collected as samples at over 70 dune crests; in the meantime, 1.6 billion 3D surface measurements of the star dune were captured by terrestrial laser scanning

… by 15 students and over half a ton of equipment.
Group of students and lecturers of the field course

Group of students and lecturers of the field course

Unloading equipment at the edge of Erg Chebbi

Unloading equipment at the edge of Erg Chebbi

ERT as geophysical measurements continued transects of the first edition of the field course. Of particular interest are the hydrologic characteristics within (i.e. under) the dune field. After visiting the relict Khettara system on the excursiong day, the group encountered a modern installation of this traditional way of water supply at Erg Chebbi, which is used to irrigate the agriculture in the oasis of Hassilabied. The water level accessed with the Khettara system was reached by the depth of boreholes drilled during the field course. These drilling verified the interpretation of geophysical measurements, which show the subsurface stratification across several dune arm. The ground water table is reflected in these ERT transects. With regards of several new ground water wells being installed along the dune field to provide water for increasing touristic economy, we hope water supply will continue to be available long-term.

Khettaras (traditional water supply system) at Erg Chebbi

Khettaras (traditional water supply system) at Erg Chebbi

Respect the dunes - wall painting at the entrance of Hassilabied

Respect the dunes - wall painting at the entrance of Hassilabied

This week, the research groups Geomorphology and 3DGeo of the Institute of Geography at Heidelberg University are conducting a field course in the aeolian sand dune field Erg Chebbi in Morocco. The current field course is the second edition of “HeidelErg.

The aim is to teach students different methods of data acquisition for physical geography, on the one hand, and to collect data for the analysis of surface and subsurface characteristics of star dunes, on the other hand. Various techniques from geophysics to 3D geodata acquisition are deployed in the frame of this field course: Sediment analysis, electrical resistivity tomography (ERT), ground penetrating radar (GPR), global navigation satellite system (GNSS) measurements, and terrestrial laserscanning. Some field days are still required to complete the multi-source dataset and report about first analyses. For now, we can give a first impression what our daily work in the sand looks like - with more to follow.

Before starting the field work, the group explored some interesting sites in the region around Erg Chebbi to get to know the stunning landscape elements of this hyper-arid region. This small excursion cannot be enough to understand the complex geomorphology and geology of Morocco - but we certainly learnt a lot from Manuel Herzog and Prof. Olaf Bubenzer, who explained the basics and latest insights along the way.

Until our next blog post, check out our occasional updates on Twitter: #HeidelErg

Interested to read more about research on star dunes? Continue here:

Herzog, M., Anders, K., Höfle, B., Bubenzer, O. (2019): Multi-method investigation of star dunes in Morocco (Erg Chebbi):topography, stratigraphy and implications for OSL-sampling. Geophysical Research Abstracts, 21, EGU2019-6950.

Herzog, M., Kanig, M., Bubenzer, O. (2019): Electrical resistivity tomography and forward modelling in hyper-arid environments – A case study from Erg Chebbi, Southeast Morocco. Zeitschrift für Geomorphologie Supplementary Issue 62 (1), 119-135. DOI: 10.1127/zfg_suppl/2019/0529.

On Feb 12, 2020, the kick-off meeting for the newly funded BMBF project LOKI - Airborne Observation of Critical Infrastructures (Luftgestützte Observation Kritischer Infrastrukturen) was hosted by the GIScience and 3DGeo research groups of Heidelberg University.

The aim of the LOKI project is to develop an interdisciplinary system that enables fast and reliable airborne situation assessments following an earthquake. A central focus is the timely overview and detailed recording of the damage to critical infrastructures, such as lifelines (bridges and roads), health care facilities and public institutions (e.g. schools). The objectives will be met by combining existing expertise in earthquake research with a variety of technologies and concepts, including machine learning, crowdsourcing, Unmanned Aerial Vehicles and 3D monitoring.

Core components of the LOKI research project and their interaction.

Core components of the LOKI research project and their interaction.

The kick-off meeting allowed the exchange of methods and expected results of the subprojects and project partners and the definition of their contribution to the overall project. Moreover, interfaces between workpackages (data, software, methodology etc.) and project partners were jointly elaborated.

Heidelberg University serves as the coordinator of the research project, which is a collaboration between several project partners. Within this collaboration, components and services developed by the individual partners will be integrated into a single system. The project partners of LOKI bring in their expertise in the following fields:

Project partners at the kick-off meeting

Project partners at the kick-off meeting

Find more details on the project website and latest project updates on Twitter or follow LOKI on ResearchGate.

The LOKI project is running from 2020-2022 and is funded by BMBF (funding code: 03G0890)

The Heidelberg LiDAR Operations Simulator (HELIOS) is an open source laser scanning simulation framework for interactive simulation and visualization of terrestrial, mobile and airborne laser scanning surveys. It can be flexibly used for teaching and training of laser scanning, development of new scanner hardware and scanning methods, or generation of artificial scan data sets to support the development of point cloud processing and analysis algorithms.

In a recent study, which was published in the Nature Research Open Acess Journal Scientific Research, HELIOS was used to compare the resolution of commercialized LiDAR to fast switching time-of-flight sensors for light detection and ranging based on hetero-integration. Find all details in the full article:

Park, M., Baek, Y., Dinare, M. et al. (2020): Hetero-integration enables fast switching time-of-flight sensors for light detection and ranging. In: Sci Rep 10, 2764 (2020), pp. 1-8. DOI: https://doi.org/10.1038/s41598-020-59677-x.

Due to its high flexibility HELIOS has already been used by the 3DGeo Research Group and other research groups for different studies and applications. Find all studies here.

If you are interested in using HELIOS for your application and research, you can download a pre-compiled latest version of HELIOS here. The corresponding wiki contains detailed information on how to set up and handle HELIOS.

Missing features in HELIOS? Why not contribute to the project on GitHub - join as developer or submit “issues” you encounter!

Follow us on ResearchGate to keep updated on the HELIOS research project!

New paper on “Multitemporal Terrestrial Laser Scanning Point Clouds for Thaw Subsidence Observation at Arctic Permafrost Monitoring Sites

Graphical Abstract

Anders et al. (2020): Graphical Abstract

The paper investigates different methods for quantifying thaw subsidence using terrestrial laser scanning (TLS) point clouds. Thaw subsidence is a slow (mm‐cm per year) vertical displacement of the ground surface common in ice‐rich permafrost‐underlain landscapes. It is difficult to quantify thaw subsidence in tundra areas as they often lack stable reference frames. Also, there is no solid ground surface to serve as a basis for elevation measurements, due to a continuous moss‐lichen cover. We investigate how an expert‐driven method improves the accuracy of benchmark measurements at discrete locations within two sites using multitemporal TLS data of a one‐year period. Our method aggregates multiple experts’ determination of the ground surface in 3D point clouds, collected in a web‐based tool. We then compare this to the performance of a fully automated ground surface determination method. Lastly, we quantify ground surface displacement by directly computing multitemporal point cloud distances, thereby extending thaw subsidence observation to an area-based assessment. Using the expert-driven quantification as reference, we validate the other methods, including in-situ benchmark measurements from a conventional field survey. This study demonstrates that quantifying the ground surface using 3D point clouds is more accurate than the field survey method. The developed methods enable a link of automated quantification and expert judgment for transparent long‐term monitoring of permafrost subsidence.

Read the full paper with open access:

Anders, K., Marx, S., Boike, J., Herfort, B., Wilcox, E. J., Langer, M., Marsh, P., and Höfle, B. (2020): Multitemporal Terrestrial Laser Scanning Point Clouds for Thaw Subsidence Observation at Arctic Permafrost Monitoring Sites. Earth Surf. Process. Landforms, DOI: https://doi.org/10.1002/esp.4833.

The source code and data of the web-based tool can be downloaded here:

Herfort, B., Anders, K., Marx, S., Eberlein, S., Höfle, B. (2020): 3D Micro-Mapping of Subsidence Stations [Source Code and Data], heiDATA, V1, DOI: https://doi.org/10.11588/data/OU8YA1.

Also, the data used in this research are openly available:

Anders, K., Antonova, S., Beck, I., Boike, J., Höfle, B., Langer, M., Marsh, P., Marx, S., (2018): Multisensor ground-based measurements of the permafrost thaw subsidence in the Trail Valley Creek, NWT, Canada, 2015-2016. Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven, PANGAEA, DOI: 10.1594/PANGAEA.888566.

This research was conducted in the frame of the PermaSAR project, which was a cooperation of the Permafrost Research Unit (Alfred Wegener Institute) and the 3DGeo Research Group (Heidelberg University) and funded by the BMWi/DLR in the framework “Entwicklung von innovativen wissenschaftlichen Methoden und Produkten im Rahmen der TanDEM-X Science Phase”.

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