EXPERIMENT IN
HYYTIÄLÄ
I've maintained an experiment in Hyytiälä
(62ºN, 24ºE) since 1993. It consists
of remote sensing and field observations.
Description
and links to data
[In Finnish].
There are accurately
mapped trees in different forests;
by Aug 2011 a total of >30000 trees are included, some trees
have
been measured allready 4 times. Characteristic to the field experiments
is that all observations are georeferenced at dm-level accuracy or
better. Recent activity in the forest:
- 2009,
Bore corer samples (ir) were taken in 1600
trees
and dbh-remeasurements (id) in over 5000 trees. Two plots with
understory, 1 ha in total, we
fully
mapped for all trees h >
0.3
m.
- 2010,
snowbreaks from Feb 2010 were mapped in 10 permanent pine plots (change
detection). Seedling stand vegetation was mapped with GPS.
- 2007-2011
forest students have mapped measured over 10000 trees during MARV#
courses.
Aerial image time-series covers
all photographs since 1946, (scale
> 1:32000).
Last film images are from 2004.
- 2006 & 2007
Vexcel UltraCAM D campaigns (1, 2.5 km)
- 2008 ADS40-SH52
campaign with in situ radiometric measurements (1 - 4 km)
- 2009 DMC I camera
tests (2, 3 and 4 km)
- 2010 Vexcel Ultracam
XP campaign (2.5 km), UAV flights
- 2011 Hyperspectral
imaging campaign (by prof. Pellikka)
There
are now seven LiDAR data sets:
2004,
2006,
2007,
2008,
2010, and 2011 (2 sets). In 2010, a consortium tested the ALS60 sensor
with a
waveform digitizer from 1, 2 and 3 km, using different digitization
scenarios. In 2011 this campaign was partly repeated. In November
2011, the first leaf-off data were acquired (Riegl LM6800 at 750
m).
A set of geodetic points has been established in the area since 2000
using
ordinary RTK and Network RTK with an accuracy of 2-3
cm.
Point set includes also some 15000 ground elevation points to verify
DEM
accuracy
in open sites. 8000 trees have been levelled in closed canopy forests
and serve
as
control points for elevation accuracy.
The forests belongs to Metsähallitus and it is thanks to
their
cooperation and long-lasting funding that Hyytiälä has this
unique
experiment. Other sources of funding, see logos above.
GOOGLE-HYYTIÄLÄ
Hyytiälä
is covered by a time-series of aerial images starting in 1946, which
are
all in one large block that has been determined accurate orientation.
Here's
a pdf by Silva
Fennica
describing how it has been done. With the imagery is possible to do
´time-travelling
in 3D` in the area. It is exciting to combine lidar with
photogrammetry.
See video-clips of the laser scanning (3
Mb, lidar pulses shot from 1000 m seen from 2500 m).(3.6
Mb Ground points) (5.5
Mb Points >20 m fm ground).
In the
summer
of 2006, we set up the first version of the GOOGLE -HYYTIÄLÄ
web-site
and interviewed people in Hyytiälä about the landscape
changes
that we observe in the 1946-2006 time period. Aerial photographs have
wittnessed
a big change in the land use patterns in Hyytiälä. Please
visit
the www site, the images are not in Finnish.
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KUVAMITT
In 1999,
I wrote the 1st version of a Visual Basic program that could
perform
multi-image matching, or least squares forward ray-intersection for 3D
point
positioning. At the time I had realized that I almost completely lack
stereo
vision so the only way to play with photogrammetry and go 3D was by
means
of monoscopic observations and ray intersection.
KUVAMITT is written in VB
6.0 (Win32) that provides the user-interface. Computer intensive
calculations are done in a C/C++ dll. This dll is linked
with the WIN32 API and Matlab dlls. VB 6.0 by Microsoft is still
somewhat alive and the support for the runtime libraries to be included
in the
future operating systems is promised
to last until 2018. KUVAMITT's
principle is that any step
in an analysis that can be visualized is visualized. This is especially
in
the favor of using it for teaching photogrammetry.
KUVAMITT's
current features include
- Block
triangulation routine that uses weighted mage observations (row, col), XYZ-,
XY- or
Z-constrained tie points (X Y and Z weights), GNSS observations and attitude
observations
(omega, phi, kappa, X0, Y0, Z0 weights) in a weighted least-square
(bundle block) adjustment.
- Monoscopic,
manual multi-image matching of up to 9 images.
- Stereocopic
mode in anaglyph. View and simple editing.
- Ortoview
mode, Fast
switching between mono, stereo, orto views.
- Digitizing
of vectors in all modes, no topology so far, just single vectors:
points
and polylines.
- Fly-through
videos:
given path output an image sequence.
- Simultaneous
use of two surface models, a DTM and aCHM, either binary
raster or
ASCII TINs. Fast TIN-2-raster conversion.
- Orthoimage
computation with a raster surface model, a DTM or a CHM.
- Semi-automatic
image matching for 3D tree top positions by template matching
- Image-based
crown width estimation using multi-scale template matching
- Tree
crown 3D modeling using adjustment of parametric crown models with
LiDAR
points under allometric constraining
- Area-based
stereo- and multi-image surface matching into a TIN. Routines for
filtering the TIN for outliers and outputting a raster surface model.
- Superimposing
3D vectors in all view-modes: mono, stereo, orto
- I/O
of R-G-B-IR, R-G-B and BW images, 8-bit and 16-bit. RAW images only.
Separate ASCII headers.
- <>Vexcel
Ultracam, DMC, and ADS40 sensor support.
- Scene
shadow
and occlusion determination using Z buffering in LiDAR data
If
you
would be interested in developing KUVAMITT into an "academic freeware"
DPW,
please contact me by e-mail. There is a 5 gB sample package and
instructions
in pdf.
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