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Some remarks on Evert-Jan Laméris workflow

Some remarks on Evert-Jan Laméris workflow by Victor Reijs is licensed under CC BY-NC-SA 4.0

Introduction

On this web page EJL workflow [Evert-Jan Laméris, 2005] based on DHM formula, is discussed. It will look at the background and provide possible feedback

Several questions are outstanding, see below purple text. If you have input, please let me know.

Background

EJL workflow is based on the DHM formula of Werkrgoep Molenbiotoop [1982]. That formula uses the principles presented in Beljaars [1979].
The workflow is:

a point cloud with surface and terrain heights (DSM and DTM) are downloaded from AHN. Preferrable to moost recent database.
the location of the wind mill is determined (using molendatabase).
Divided the area (in 8 rings of 50m wide: total radius of 400m) in 288 sectors (36 sectors in each main wind direction [8 different colors], resulting in 1 to 8 sectors per ring-segment):
by using the standard DHM formule (using n=50 and c=0.2), the H_DHM is calculated
all H_DHM are being normalised by dividing with the sail-arm length
the highest normalised H_DHM in each sector is determined. Each sector gets a category allocated (1 to 5), based on this highest normalised H_DHM
For each of the 8 wind directions, the categories per ring are summed and weighted averaging has been used to have for each ring a comprable value.
All per ring weighted average are summed for each wind direction, and this indicates the wind obstruction per wind direction for that mill.
So all the influences (normalised H_DHM) are evaluted together for the location of the mill (no interaction between indivudual obstacles).
In general it is a qualitative methdology (so comparing between wind mills becomes easier).

Of course different analysis is possible by varying sector layouting, averaging/summing/weighting and grouping (certainly because AHN5 has a resolution of 0.5m). As the database is queried with SQL, these different analysis can relativly easy be implemented.

Methodology usage

This methodology has been used for all traditional windmills within some 5 Dutch counties.

Some ideas for extension to the workflow

At this moment the influence of sequence of obstacles is simply summed. One could of course also use the SpeedFactor (by using Steve Temple's method) in the path over all the obstacles towards the mill in a certain direction. In that way the resulting SpeedFactor is determined. This should be possible using a proper SQL querying command.

References

Laméris, Evert-Jan: Ruimte voor Molens met Geo-Informatie. In: https://onderzoek.molenbiotoop.nl/ (2005), Accessed 7 January, 2025.

Acknowledgements

I would like to thank people, such as Evert-Jan Laméris, and others for their help, encouragement and/or constructive feedback. Any remaining errors in methodology or results are my responsibility of course!!! If you want to provide constructive feedback, please let me know.

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Major content related changes: January 7, 2025