----- Forwarded message from Sive Finlay <[email protected]>
-----
Date: Wed, 23 Jan 2013 05:27:24 -0500
From: Sive
Finlay <[email protected]>
Reply-To: Sive Finlay
<[email protected]>
Subject: Replicates for error checking when
digitizing landmarks
To: [email protected]
Dear all,
I am studying morphological convergent evolution in the skull and limb
shapes of tenrecs compared to other small mammals. I have approximately 100
species and aim to both measure and photograph 10 representatives of each
species. I have a query relating to the optimal way to check for error when
digitizing landmarks on my photographs.
From my reading of other studies, I've come up with 3 possible ways to
approach error checking;
1) Take one photo of each specimen, make copies of that one image, digitize
the same landmarks on each copy and then measure the variability between these
landmarks to estimate digitizing error.
2) Take multiple photos of each specimen (is 3 enough to aim for in this
case?) and use these to digitize landmarks separately on each image
3) Take multiple photos of each specimen but re-position the skulls/ limbs
between every photo
The aim of options 1 and 2 would be to account for error in my own ability
to be consistent in digitizing the landmarks. In contrast, any landmark
variation with the option 3 approach would be a combination of both digitizing
skill error and discrepancies associated with how the specimens are positioned
for the photographs (e.g. if they're not completely flat in the plane of
focus).
The issue with this 3rd option would be that it's far more time consuming
since each specimen would have to be positioned and photographed on 3 separate
occasions while options 1 and 2 only require me to set up each picture
once.
Given that my aim is to collect 1,000 specimens (10 replicates of 100
species), I would be very grateful for any advice on which error checking
approach is practical or necessary. In addition, any modified or alternative
suggestions for error-checking approaches would be very much appreciated.
Thank you!
Sive
-- Sive Finlay
IRC EMBARK Initiative Postgraduate Scholar
Macroecology and Macroevolution Research
Group
Zoology
building
----- End forwarded message -----
