False colour NDVI image

NDVI investigations of compost-enhanced crops

I made a couple of NDVI images of the beans which had been greatly improved using compost compared to those grown without. The principles of NDVI as based on that

Generally, healthy vegetation will absorb most of the visible light that falls on it, and
reflects a large portion of the near-infrared light. Unhealthy or sparse vegetation reflects
more visible light and less near-infrared light. 1

Knowing that, it’s possible to see in the NDVI image that the compost-grown beans do seem to be reflecting more IR relative to visble light, I find this easier to qualify from the greyscale image Continue reading


  1. Understanding the NDVI PDF
Beans showing effects of compost extract

Remarkable win on beans with compost extract

Last year we made compost and compost extract for use in the polytunnels. The extract was also looked at with the microscope. Most of the compost after making extract was used in polytunnel which has tomatoes in it. These look healthy and were praised by another local gardener, but there’s no control. However, we did have a control on the extract applied to the beans in another polytunnel.

If you look at the picture at the head of this post, on the RHS of the picture is the control. This is what we would have grown normally.

in the middle on the top you can just see a blue ribbon which is where application of the compost extract stopped. On the left are the plants where compost extract was applied to the ground, it ran out at the blue ribbon point. Same plants, same time planted, and the same set of seeds. The difference in vigour, height of growth and yield is remarkable and clearly to be seen. Continue reading

The Sainsonic AP510 APRS tracker can work well

As long as you recognise that the stock antenna is truly dire. And you’re prepared to fiddle a lot to get the AP510 and software going. This is not something that works out of the box. As supplied from Ebay in April 2016 the firmware of this didn’t match the software, in fact the firmware was too old. Cue much frustration and turning off and on to try and get it to talk. No dice.

Sainsonic AP510 description

Do what this guy says he has a treasure trove of the files in the links to the youtube post. It worked for me. I had to flash the firmware before my box would talk to the Sainsonic config software, and without doing that this device is no use at all.

Now if you can get an integrated GPS, APRS tracker, 2m rig for £78 it’s a great deal, if you can’t configure it it’s a rotten deal. But it worked for me in the end. There’s much to like, it’s small, it has its own battery, the price is right etc. There are things not to like – the male SMA on the board. SMAs are fragile, that pin is gonna break after about 500 cycles, which is why it’s nice to have the plug on the cable or the rubber duck aerial so you get to change that rather than the rig. Oh and the USB connector is a 3.3V RS232 connector, not a USB connector, though it can use a mini USB connector to a normal USB outlet to charge.

Sainsmart AP510

Sainsmart AP510

So I configured it and fired it up and it sort of works, well, out to about 200m for a J-pole vertical in my loft. Now I admit a J-pole with its somewhat live coax even after a CM coax choke doesn’t belong in the cluttered environment of the loft and I’ll change it for a Diamond X-30 or the like outside at some point, but I have a receive igate on it and it serves other mobile APRS stations okay enough, and serves me up to about 500m in the town with a Kenwood THD7. Continue reading

A short survey of sparrows in Glastonbury

I was in Glastonbury, Somerset, and the house sparrows have started calling at nest sites there, They haven’t started in Ipswich. So I tried the audio recorder/GPS track surveying method. Each of the flags is where there was a male calling, or a male was sighted, along the lines of the BTO survey protcol 1

I covered a decent area, but not as thoroughly as I thought I had done. The sparrows seem in good heart, however, a more continuous coverage than I feel they are in Ipswich, where the colonies strike me as more fragmented. We will see.

My general impression was that sparrows are doing better in Glastonbury than many parts of Ipswich. The route I took left residential areas for the high Street, I know there are sparrows in Northload street so the two clusters might join.


  1. Protocol for censusing urban sparrows, DeLaet, Peach and Summers-Smith, British Birds, 104, May 2011, p255 ff

Bird surveying in the field using GPS

The Ipswich RSPB Local Group is looking at surveying Ipswich’s house sparrows, ten years on after I took part in the first Ipswich Sparrow Survey. Most bird surveys cover a wide, fairly homogeneous area and avian subjects that are mobile over several hundred metres, or specific colonies. Surveying sparrows in the heterogeneous urban environment, with subjects that stay within 70m of the nest site when feeding young are a different kind of challenge.

We didn’t have the benefit of this BTO House Sparrow Survey protocol 1. As such the results show sample bias from the observer locations, survey effort and the difficulty to getting negative reports. However, it did answer the question ‘where are there sparrows in Ipswich?’, although not the question ‘where are all the sparrows in Ipswich’. It also answered the question ‘where are there no sparrows’ although the sparrowless areas were not exhaustively surveyed. Proving a negative is hard, though the BTO paper shows the way.

In the intervening time I solved the need to create waypoints on a handheld GPS and announce them to tie the audio to the location. Modern audio recorders contain clocks and timestamp the recording, this can be synchronised with the GPX tracks created by the GPS handheld. Smartphone applications like viewranger can also create GPX tracks. However, although a smartphone does many things it doesn’t do any of them very well.

The same trip tracked using Viewranger on a Samsung Android phone versus a Garmin Vista HCx. each machine was in different outside pockets of a coat at the same height above ground. The lighter red tarce is the Garmin which follows the paths better

The same trip tracked using Viewranger on a Samsung Android phone versus a Garmin Vista HCx. each machine was in different outside pockets of a coat at the same height above ground. The lighter red trace is the Garmin which follows the paths better

I set the Samsung to give the most precise location. The issue doesn’t seem to be as simple as the Viewranger Samsung app updating slower than the Garmin, there are enough points, but they aren’t in the right place, particularly when the border trees by the road and railway line

the save trace showing the trees

the save trace showing the trees

The aim of all this was to write a web app to record sparrows in the field. However, it turns out that the Location API is very hit and miss. Sometimes I got 20m accuracy. Sometimes I get 3km accuracy, and I can’t easily see how to fix that, having already selected high geolocation accuracy. If I can’t do that for myself, I certainly can’t support other people using it on two different operating systems and on some mobiles that may not actually have a GPS receiver.



  1. Protocol for censusing urban sparrows, DeLaet, Peach and Summers-Smith, British Birds, 104, May 2011, p255 ff
Wolfson board mounted onto a Pi model A

Timed Audio Field Recorder with a Raspberry Pi Cirrus Logic Audio Card

The problem is still the same as it was this time last year – the birds get up before I do in the Spring and I can only be one place at a time. Automatic recording devices let me scout locations in parallel.

A timed field recorder needs to be cheap, because somebody might nick it, it needs to be weather-resistant because it’ll be stuck outside, and it needs to be low-power, because 13A mains sockets are rare outside. Oh and it needs to be standalone, and not part of some cloud, because mobile Internet is ratty and expensive.

tl;dr the hardware performance is good but software support is dire. You can make this work but it isn’t fun at all. If you can use something like a USB stereo audio in board then do it rather than use this Cirrus Logic Audio Card, particularly if you have mains power available. I like the Behringer UCA202 and it works with the Pi

A Raspberry Pi and A Wolfson audio card sort of fitted the bill, but the Wolfson Audio card is no more. I say sort of, because I’m still looking at about £70 for a Pi 1, the audio card and enough odds and sods to power it. You can buy a Zoom H1 for about £80, although there’s still a bit more cost in powering it for long times, keeping the water out and making up some gizmo to pretend to be you pressing the big rec record button early in the morning.

But with the Pi I get to drive the recorder via cron and ssh, and transfer the files via the internet or mobile data in some places. Even if I don’t get a case, though they are to be had for the Pi/CL Audio card combination…

Continue reading


  1. HiFi world clock it in at £220!