Interpine Innovation

How Accurate Can We Expect Routine Location of Plots Under Forest Canopy Using GPS
24/02/2012 1:50:00 p.m.
Recently, we looked at GPS Precision (EPE). A few questions were also raised about plot location and I thought it might also be good to look at how accurate we could expect to locate the survey point inside the forest under a range of conditions and forest canopies. The dataset used contains 320 survey points located throughout New Zealand. A recreational grade GPS (Garmin Map 60CSX) was used to locate the survey point in the field. At this point a survey grade Trimble ProXT GPS unit was raised to 5m and recorded 300-500 data points over a period of 20mins to 3 hours. This was then post-processed to "geo-fix" the actual field plot. Precision of the fix from the survey grade GPS was usually within 2m.  See this earlier article for more information. Figure 1 shown below displays the horizontal distance from the intended survey point location to that actually fixed in the field using the...

GPS Accuracy Estimate (EPE) What is It ?
7/02/2012 1:58:00 p.m.
The use of recreational grade GPS (for example Garmin 60csx or Garmin 62S) is now standard practice for the location of forest inventory plots in New Zealand and Australia. We recently reviewed a few questions regarding the accuracy and precision of these GPS units, with many in the industry not understanding the measure of precision displayed to the user. If the GPS displays an Accuracy of 10m, does this mean it is 10m from the actual / absolute location? MOST DEFINITELY NOT !! Firstly it is a measure of precision and in no way indicates accuracy. GPS's display to the user an estimate of position error (EPE). An EPE is displayed on most recreational GPS devices, although there is no general specification on what this should display between manufacturers or in some cases models from the same supplier, so an EPE from a Garmin device cannot be directly compared to...

How Effective are LiDAR-based Forest Inventory Systems ?
9/12/2011 2:23:00 p.m.
ForestTech 2011 has held in late 2011 in both Australia and New Zealand. Interpine's Jonathan Dash and Hamish Marshall presented a discussion on Interpine's involvement in a range of trial work relating to LiDAR analysis. A quick overview of use and role of LiDAR in forest inventory systems was covered. Then a review of some of the practical decisions / advice we ourselves have worked through while planning and interrogating LiDAR datasets, including sample design, installing ground control plots, allocation of plot size and dealing with edge plots. Finally a brief summary example was given on its use in improving accuracy or reducing cost of traditional rule based sample design inventory carried out in the eastern BOP of New Zealand. Acknowledgements are given to Future Forest Research, PF Olsen Ltd, Ministry for the Environment, Susana Gonzalex-Aracil (Interpine Post-Grad Research Intern), and Outline Imagery for this assistance during some of the...

Interpine Offers Forestry Orientated LiDAR Analysis Training Course
17/08/2011 4:00:00 p.m.
After successfully completing our first Forestry Orientated LiDAR Analysis course to the final year students at the University of Canterbury in June 2011, Interpine is now offering this to the wider industry. This is an introductory course learning how to manipulate and process LiDAR datasets, with a specific focus on forestry outputs. The course is lecturer is Dr Hamish Marshall. The course covers the topics with hands-on labs and presentations, whereby students work through real world examples using New Zealand LiDAR derived datasets using the software such as FurgoViewer and FUSION. From getting started with LiDAR data, creating surfaces models of terrain or vegetation, to single tree or plot extraction datasets and calculation of LiDAR forest metrics, there will be something to learn for all those interested in taking the next step in utilising their own LiDAR datasets. If you would like to know more or register your interest in...

Forest Canopy Drip-line Buffers for the Forest ETS Mapping
18/09/2010 12:21:00 a.m.
There are a number of guidelines and rules to consider when mapping forest areas when applying to be involved in the forestry ETS (Emissions Trading Scheme). One that is often missed by inexperienced forest mapping providers is the need to "position the polygon along the canopy drip-line at maturity". Simple mapping tools such as that provided by the MAF Online ETS tool only allows users to draw lines around forest based on the imagery shown. However this imagery could already be several years old, or the forest itself in the imagery has not yet reached maturity, potentially resulting in an underestimate of the planted forest "net stocked area". Figure 1 shows how even a small buffer of 3m, add a continuous addition of net stocked area to the entire stand boundary.       MAF suggests buffering up to 4m based on the stand age (compared to the date of imagery) and species....

High Precision Sub-meter GPS Performance under Forest Canopy in NZ
17/09/2010 11:24:00 p.m.
Interpine has been working with LiDAR ground control survey for several years now. To ensure that the LiDAR data is compared correctly with the ground control measurement data, high precision sub-metre GPS units are used to fix the location of the plot centres (Trimble ProXT GPS Units). Combined with the Allegro MX or Trimble Nomad handheld computers and Terrasync software these units collect detailed location and GPS satellite network information while onsite. This allows the data to be "post processed" bringing the accuracy of the plot centre fix in optimum conditions to less than 1m. However we all know the forest is not the easiest place to operate high precision GPS units so I thought we might share some our findings and suggestions. The project objectives were to geo-fix the plot centre locations within 2.5m. After some trialling of the Trimble ProXH (sub-foot) and Trimble ProXT (submetre) units, it was...

Mapping Your ETS Forests - Overview
17/09/2010 3:50:00 p.m.
If you're entering the forestry Emissions Trading Scheme (ETS), you are likely to have been asked to map out your forest land. This is the first step used to estimate the total amount of carbon stored (i.e. the forest "carbon stocks"). Apart from determining your forest land area, it also confirms to the Ministry of Agriculture and Forestry (MAF) that you have legal rights to the forest area mapped. MAF will also overlay the mapped area with historical aerial photos and satellite imagery reviewing the classification of forest land type (i.e. comparing the forest cover at 1990), to ensure it is correctly allocated into Post-89 Forest Land or Pre-1990 Forest Land. An example of a forest map produced for application into the forestry ETS is shown below. When is a Map Required?Each MAF application process will clearly outline the requirements for mapping and should be consulted before deciding if...