Tag Archives: sussex

Aerial imaging

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Cost-effective environmental imaging services combining camera drone and cloud technology

As a drone pilot and operator registered with CAA in the UK I’m able to offer a variety of commercial services in open countryside locations, where a full PfCO is not required.

Mapping

On one privately owned site in the Surrey Hills AONB I mapped 32 hectares (79 acres) of part ancient, mixed broadleaf woodland.

Thousands of individual images were stitched together to create an orthomosaic, which was then exported as individual GeoTIFF tiles compatible with GIS software. Very high resolution single images can also be generated (2cm/pixel).

Mapping missions were flown at different times of year to observe seasonal variation.

Analysis

Spectral analysis techniques allow aerial imagery to be used for environmental monitoring at landscape scale. The image below compares visual spectrum vs. enhanced NDVI processing to study plant health.

Visual spectrum vs. NDVI showing replanted woodland

Change detection

Orthomosaic images facilitate accurate measurement to inform effective land management. The aerial map below quickly measured the extent of a heathland fire at Thursley Common NNR in Surrey for Natural England.

Aerial drone map showing extent of Thursley NNR heath fire

Monitoring

Below is an aerial survey of a Homes England residential development at the point where a new access road crosses a river valley intended to form a ‘green corridor’ for wildlife. Orthomosaic, NDVI and elevation visualisations are compared.

This short animation shows the image resolution (~2cm/pixel) attained from the same drone survey mission flown at an altitude of 100m.

Timelapse

By layering orthomosaic images created in different seasons it’s possible to create a wide area timelapse sequence, as shown below.

Video

More conventionally, the video below shows scenes from a Bluebell wood in early spring. Bluebells are an attractive ancient woodland indicator species.

Drone vs. satellite

Drones and satellites offer complementary technologies for aerial imaging, but camera drones enjoy a few advantages:

  1. Resolution
    Satellites cannot compete with drones for detail. Satellite images will allow you to see individual trees, but with a drone it’s possible to distinguish each leaf.
  2. Perspective
    Satellites are restricted to flat overhead perspectives. A well-operated drone can film or photograph any subject from almost any angle. This can assist in the capture of digital elevation models using 3D point clouds.
  3. Urgency
    You don’t need to wait for cloud cover to clear before flying a drone survey! If clouds obscure your satellite image you have no option but to schedule another attempt… and cross your fingers.

White Admiral Watch: Rollo’s Story

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A tale in tweets following the life of Rollo, a White Admiral butterfly caterpillar, offspring of Camilla

As Rollo slumbers a brief interlude follows…

We return to the star of our show…

Rollo’s close neighbour catches a chill…

Spring returns to the wood…

White Admiral Watch pays tribute to Eric Carle, author of ‘The Very Hungry Caterpillar’…

But not all is well…

The reason for Rollo’s delayed development becomes clear…

Search #WhiteAdmiralWatch on Twitter for more!

White Admiral Watch

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White Admiral butterfly metamorphosis: from larva to prepupa to pupa to imago.

In Sussex during the COVID-19 epidemic of 2020 I followed one very special butterfly through pupation to emergence

The White Admiral (Limenitis camilla) is a large woodland butterfly which glides effortlessly along forest rides. Its numbers in the UK have rebounded since the First World War, possibly due to the cessation of coppicing which, unusually, has benefited this species since its larvae require Honeysuckle growing in shady woodland.

28 May

My first, long awaited, encounter with ‘Camilla’ came on 28 May when my many searches of Honeysuckle vines finally bore fruit and this magnificent creature suddenly greeted me.

White Admiral (Limenitis camilla) 5th instar caterpillar on honeysuckle (Lonicera periclymenum).

White Admiral caterpillars are entirely dependent on Honeysuckle for their survival, feeding on its leaves through all five larval instars and hibernating within their folds.

At more than 2 cm in length this was a fifth and final stage caterpillar, exotic in appearance compared to the majority of British butterfly larvae, adorned with branching red spines along its back and resting in a raised serpentine position.

31 May

When I returned 3 days later Camilla was already preparing to pupate, hanging beneath a Honeysuckle leaf, suspended from her hind claspers attached to a pad of silk.

White admiral (Limenitis camilla) prepupa suspended from honeysuckle (Lonicera periclymenum).

2 June

48 hours later the pupa was now fully formed, with two prominent horns on the head and an odd protrusion further back.

“The pupa bears a close resemblance to a profile portrait of Punch.”

– Frohawk (1924)

White admiral (Limenitis camilla) pupa suspended from honeysuckle (Lonicera periclymenum). Day 1.

7 June

The pupa darkened up a little in the next few days, its undulations mimicking the Honeysuckle leaves quite convincingly.

White admiral (Limenitis camilla) pupa suspended from honeysuckle (Lonicera periclymenum). Day 6.

For the next two weeks few visible changes occurred and the weather turned cold and wet. A marauding army of small birds came and went, leaving Camilla thankfully undisturbed.

23 June

Around Day 22 the folded wing veins became a bit more pronounced beneath the pupal case and its body seemed to have plumped up a bit. Warm, sunny weather had returned to the woodland glade.

White admiral (Limenitis camilla) pupa suspended from honeysuckle (Lonicera periclymenum). Day 22.

24 June

Revisiting on the morning of Day 23 I found Camilla had darkened up overnight, turning from green to brown, signalling that ‘eclosion’ of the adult butterfly was imminent.

White admiral (Limenitis camilla) pupa suspended from honeysuckle (Lonicera periclymenum). Day 23 (AM).

By 5pm that afternoon my ‘White’ Admiral was now distinctly black!

White admiral (Limenitis camilla) pupa suspended from honeysuckle (Lonicera periclymenum). Day 23 (PM).

From a different angle the butterfly’s wing structure and patternation could clearly be seen.

“Before emergence it turns to a bronze-black all over, losing almost all the metallic lustre of silver-gilt; the white wing markings of the imago show pale amber colour through the pupal skin.”

– Frohawk (1924)

White admiral (Limenitis camilla) pupa suspended from honeysuckle (Lonicera periclymenum). Day 23 (PM).

I was hopeful the adult butterfly would emerge that evening and so remained until well after dusk, but as it grew dark I was forced to return home for the night.

25 June

Back on site very early next morning I was relieved to discover that the big moment had yet to arrive.

Camilla remained suspended from the Honeysuckle leaf until 09:11 on Day 24 when she suddenly popped out of her chrysalis in the blink of an eye, annoyingly while my back was briefly turned!

White admiral (Limenitis camilla) imago newly hatched. Day 24.

Camilla luxuriated in the warm morning sunlight streaming through the oak canopy, slowly expanding her glorious wings as she clung to the vacant ‘exuvia’.

White admiral (Limenitis camilla) imago newly hatched. Day 24.

By 10:50 her wings were fully expanded and at 11:12, two hours after emergence, she clambered nimbly up onto the Honeysuckle leaf which had supported her pupa through sun and rain, heat and cold, for the past 24 days. It would now become her launching pad.

White admiral (Limenitis camilla) imago shortly before first flight.

And then 8 minutes later, at 11:20 she flew for the first time… and was gone!

Video showing newly emerged White Admiral (Limenitis camilla) butterfly drying its wings before takeoff.

Except that I strongly suspect she hung around…

I only witnessed one other adult White Admiral in the wood that summer. The individual photographed below frequented Bramble blossom within metres of Camilla’s hatching site, sunning itself on the woodland floor nearby and alighting on Honeysuckle, likely assessing suitable spots to lay her eggs for the next generation of White Admiral caterpillars to emerge.

White admiral (Limenitis camilla) butterfly nectaring on bramble flowers.

To be continued…

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Toads on roads

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Common toad (Bufo bufo) crossing a road at night on migration to breeding pond. Sussex, UK.

After emerging from hibernation in early spring common toads (Bufo bufo) migrate back to their breeding ponds at night. Sometimes this involves crossing busy roads and many toads are sadly hit and killed by passing cars.

Each year volunteers working with charities such as Froglife and local Amphibian and Reptile Groups attempt to ferry migrating toads, frogs and newts to safety at known crossing points.

Toad crossing signage. Sussex, UK.
Common toad (Bufo bufo) juvenile recovered at road crossing on spring migration. Surrey, UK.
Toads retrieved from road in a bucket

Male toads grasp females in a position known as ‘amplexus’ as they attempt to fertilise her eggs. Often a mating pair can be found together before they reach the nearest pond. When this happens males hitch a free ride!

Common toads in amplexus while crossing a road on spring migration

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