The Geometer: A New Device for Recording Angles in Visual Surveys


  • Rikke Guldborg Hansen Greenland Institute of Natural Resources
  • Daniel G. Pike
  • Baldur Thorgilsson
  • Thorvaldur Gunnlaugsson
  • Jack Lawson



geometer, declination, clinometer, visual survey, survey software


The Geometer is a new handheld USB device that facilitates a relatively accurate measurement of the declination to a target with instantaneous recording of this and other data. The Geometer offers several advantages over traditional clinometers used in aerial surveys, including easier target pinpointing and tracking, more consistent angle measurements, and integration with software data collection packages. In this note we provide technical specifications for the device and its associated software, and describe a new aerial survey data collection programme that takes full advantage of the features of the Geometer. We have tested this device extensively during aerial surveys and highlight the utility of the hardware as well as ways in which the technology could be improved.


Borchers, D. L., Marques, T., Gunnlaugsson, T. and Jupp, P. (2010). Estimating Distance Sampling Detection Functions when Distances Are Measured with Errors. Journal of Agricultural, Biological, and Environmental Statistics, 15(3), 346–361. DOI:

Borchers, D. L., Pike, D. G., Gunnlaugsson, Th. and Víkingsson, G. A. (2009). Minke whale abundance estimation from the NASS 1987 and 2001 aerial cue–counting surveys taking appropriate account of distance estimation errors. NAMMCO Scientific Publications, 7, 95–110. DOI:

Buckland, S. T., Anderson, D., Burnham, K., Laake, J., Borchers, D. and Thomas, L. (2001). Introduction to distance sampling estimating abundance of biological populations. Oxford University Press.

Hansen, R. G., Boye, T. K., Larsen, R. S., Nielsen, N. H., Tervo, O., Nielsen, R. D., Rasmussen, M. H., Sinding, M. H. S., & Heide-Jorgensen, M. P. (2019). Abundance of whales in West and East Greenland in summer 2015. NAMMCO Scientific Publications, 11. DOI:

Hiby, A. R. and Hammond, P. S. (1989). Survey techniques for estimating current abundance and monitoring trends in abundance of cetaceans. Report of the International Whaling Commission, Special Issue 11, 47–80.

Lawson, J. W. and Gosselin, J. F. (2018). Estimates of cetacean abundance from the 2016 NAISS aerial surveys of eastern Canadian waters, with a comparison to estimates from the 2007 TNASS. SC/25/AE/09 for the NAMMCO Scientific Committee.

Leaper, R., Burt, L., Gillespie, D. and Macleod, K. (2010). Comparisons of measured and estimated distances and angles from sightings surveys. Journal of Cetacean Research and Management, 11, 229–237. DOI:

North Atlantic Marine Mammal Commission (NAMMCO). (2013a). Report of the NAMMCO Scientific Committee Working Group on Survey Planning. NAMMCO Annual Report 2012, 392–475. Retrieved from

North Atlantic Marine Mammal Commission (NAMMCO). (2013b). Report of the Nineteenth Meeting of the Scientific Committee. NAMMCO Annual Report 2012, 263–550. Retrieved from

North Atlantic Marine Mammal Commission (NAMMCO). (2016). Report of the NAMMCO Scientific Committee Survey Planning Working Group. NAMMCO Annual Report 2015, 305–318. Retrieved from

Pike, D. G. (2013). Aerial survey: State of the art and recommendations for the next T-NASS. NAMMCO Annual Report 2012, 411–441. Retrieved from

Pike, D. G., Gunnlaugsson, T., Mikkelsen, B., Halldórsson, S. D., Vikingsson, G. A., Acquarone, M. and Desportes, G. (2020). Estimates of the abundance of cetaceans in the Central North Atlantic from the T-NASS Icelandic and Faroese ship surveys conducted in 2007. NAMMCO Scientific Publications, 11. DOI:

Pike, D. G., Gunnlaugsson, T., Sigurjonsson, J. and Vikingsson, G. A. (2020). Distribution and abundance of cetaceans in Icelandic waters over 30 years of aerial surveys. NAMMCO Scientific Publications, 11. DOI:




How to Cite

Hansen, R. G., Pike, D. G., Thorgilsson, B., Gunnlaugsson, T., & Lawson, J. (2020). The Geometer: A New Device for Recording Angles in Visual Surveys. NAMMCO Scientific Publications, 11.

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