Ian Lockwood

MUSINGS, TRIP ACCOUNTS AND IMAGES FROM SOUTH ASIA

Archive for May 2018

Landcover Changes in the Palani Hills-A Spatial Study

leave a comment »

Lenny & Prasen on Dolphin’s Nose with Perumal peak in the far left. A panoramic composite image from January 2016.

The grasslands mapping project that took shape at the plantations conference in Kodaikanal in December 2014 produced a report that was published earlier this year. This is important work and represents the combined efforts of several disparate individuals, organizations and funding agencies. The preliminary visual assessment of Landsat imagery by the author showed that satellite data held spatial evidence of dramatic land cover change in the Western Ghats and Palani Hills but that it needed to be quantified. Robin Vijayan of ISER Tirupati put into motion a study in 2016 with key field work and spatial analysis being done by M. Arasumani and Danesh Khan. Further academic guidance was provided by Arundhati Das, Milind Bunyan and several others. Bob Stewart & Tanya Balcar, of the Vattakanal Conservation Trust, provided key insights on shola regeneration in plantations-the topic that originally brought everyone together. INTACH and ISER Tirupati helped provide funding of the field work. The Tamil Nadu Forest Department was an important stakeholder and helped provide permissions for the field work. Prasen Yadav joined the project to document the work and produce a video of the findings. The study was peer reviewed and published in January 2018.  It is publicly available on PLOS One, including access to all the tables of data and charts (see link below).

My involvement with the grasslands mapping brings together several interests and is the latest chapter in my ongoing interest and love affair with the Palani Hills. An alarming conclusion of the study is the great extent to which the montane grasslands have been taken over by non-native trees and weeds. Those of us who have been walking in the hills have had a sense of this but the satellite images providing damning proof. It is also clear that the plantations have spread far beyond the original boundaries that they were originally designed to be in. Most of the southern escarpment has a fire line etched into its grasslands and now plantations species are spreading beyond this boundary and down the steep slopes of montane grasslands. This leads to clear conclusion that where possible efforts need to be made to preserve these last remaining vestiges of montane grasslands. The challenge is that, in spite of the surprising resilience of shola tree species, the last montane grasslands are being steadily consumed by plantation (and some shola) species.

Our study concludes:

  1. Identify and conserve core grasslands: Core grassland areas consist of a few to many hectares of grassland encompassing hillocks, streams, marshes and rock outcrops. These areas, even when nestled in a plantation matrix, should be protected and form the core around which grassland restoration efforts should focus.
  2. Check invasion in sparsely invaded grasslands: These areas are often characterized by young plantations located in grasslands where grass cover is still extensive. Here, we recommend physical removal of invasive species. Forest departments often have access to significant funding through the Compensatory Afforestation (Bill passed in 2016) funds and these could be utilized for these activities. Such funds could be used for the restoration of marshes, existing grasslands and to manage the invasive plantations.
  3. Review indiscriminate removal of mature plantations: Mature plantations often have native shola forest regenerating under them and lack native grass cover. Grassland restoration here is likely to be very resource-intensive. Conservation efforts should focus on sparsely invaded and pristine grasslands. In mature plantations, we recommend conducting experimental or controlled studies (like at Vattavada, Munnar Kerala), perhaps also examining the role of fire, and monitoring soil and moisture conditions in these areas. Moreover, removal of mature plantations could stimulate regeneration of plantation species from saturated soil seed banks. Monitoring of these areas is important to assess the effectiveness of plantation removal.
  4. Contain agriculture: Our field surveys indicate that paddy cultivation has been discontinued in some marshes. Given the critical role of these marshes in regulating local hydrology, efforts should be made to contain agriculture to the current extent and restore these marshes using a community-led conservation effort.

Several other writes have reviewed the PLOS article in the popular press and I have listed articles in the Wire by Janaki Lenin, Mohan Rao in the Hindu and Pendharkar, Vrushal in Mongabay.

This year is a special year since it marks the cycle of Kurinji (Strobilanthes kunthianus) blooming that only happens every 12 years. Kurinji plants, more than any other grasslands species, are closely associated with healthy montane grassland systems. The extent of this year’s flowering will be a good gauge of the health of the grasslands of the Palani Hills.

My next personal chapter in this process to better understand the landscape and ecology of the Palani Hills is to present and share an exhibition of photographs and annotated maps at DakshinaChitra, Chennai this July. The next post will highlight this significant endeavor.

Southern escarpment on a very clear day looking west to the Agamalai range and beyond. January 2016.

REFERENCES & FURTHER READING

Arsumani, M. et al. “Not seeing the grass for the trees: Timber plantations and agriculture shrink tropical montane grassland by two-thirds over four decades in the Palani Hills, a Western Ghats Sky Island.”  PLOS One. January 2018. Web.

Lenin, Janaki “You’d Think Cutting Kodai Plantations Will Save Its Grasslands. It Won’t.” The Wire. 19 September 2017. Web.

Lockwood, Ian. “Mapping Montane Grasslands in the Palani Hills.” Ian Lockwood Blog. August 2016. Web.

“         “Land Cover Changes in the Palani Hills: A Preliminary Visual Assessment.” Ian Lockwood Blog. 4 April 2014. Web.

Montanari, Shaena (& Prasenjeet Yadav). “Breathtaking Sky Islands Showcase Evolution in Action.” National Geographic. 11 August 2017. Web.

Pendharkar, Vrushal. “Palani Hills: Where have the grasslands gone?” Mongabay. 20 February 2018. Web.

Rao, Mohan. “Missing the grass for the trees in Western Ghats.” The Hindu. 17 January 2018. Web.

Yadav, Prasenjeet. “Save our Shola Grasslands.” YouTube. Web-Video. 16 September 2017.

Written by ianlockwood

2018-05-28 at 11:56 pm

Drone Mapping & Modeling in Pelawatte 101

leave a comment »

3D April 6 flight_3D_model

3D model of the OSC created on DroneDeploy based on data from the April 6th flight (approximately 81 images).

For the last year or so it has been my goal to use drones to better study areas and analyze patterns of land use and vegetation cover. I was first inspired by the work that IWMI was doing to map crops, irrigation and drainage basins using their fixed wing drone (see articles below for references). During the last two years there has been a good deal of excitement of using drones/UAVs for geospatial applications and I am entering the field relatively late. One of the notable highlights of Sri Lanka’s first GIS Users conference held in February 2018 was a presentation on the use of consumer-level drones to map small areas. A Sri Lanka Ministry of Defense Research & Development team demonstrated in real time how easy it was to program a flight path, put a drone up, collect data and then process it so that it could be used for analysis using GIS. Based on their example and the advice of IWMI’s GIS team, I have been working to use the school’s Phantom III Advanced drone to map our campus as well as the nearby Diyasaru wetlands.  This post share some of the results as well as my workflow.

Poster of April 6th drone map of the OSC campus, created on ArcMap 10.5.1.

Results from the May 19th drone flights using PIX4D. This is a composite of two different flights, each with about 30-50 separate images that have been mosaiced and geo-referenced here. If you look closely you will see the OSC Class of 2019 DP Geography class on the west side of the field. Also note the missing large mahogany tree north of  the pool that was regrettably cut down by the neighbors between the two flights.

A Work Flow for OSC

  • Step 1  Having a drone is essential and many of the common consumer models can be programed to fly a set flight plan. We used a DJI Phantom III Advanced model that is the older of our two drones (it has already had several major accidents and gone underwater at least twice). The drone needs to be working properly and the micro SD card should be formatted before running the mapping flight. We have been doing a very short test pre-flight on the DJI app that we control the drone with.
  • Step 2 You need an app to establish the flight path and program the drone to fly and take pictures at established intervals. We started with a trial version of DroneDeploy and have now loaded in a trial version of PIX4D. Unfortunately, the licensed copies of both of these software bundles are prohibitively expensive for small non-commercial programs like ours and I will have to work out a long-term solution so that students can continue the mapping that we have started. The proposed mapping area needs to be loaded into the drone using the app. For DroneDeploy I made the flight plans on a desktop computer (in the DroneDeploy website) and then imported them onto the phone app that is hooked up to the controller. There are several parameters to pre-set such as the overlap flap area, flight altitude etc.  The higher the altitude, the more accurate and less distorted the stitched imagery but it is coarser (less detailed). For PIX4D I have been setting the flight area on my phone in the field.
  • Step 3 At your location you can launch the drone from a cleared area. We use the school field where there is plenty of room and a clear line of sight between the controller and drone (though it is flying by GPS, apparently). When you have got the drone and controller (with a phone interface) unit set up, you are ready for the flight. On DroneDeploy you import the plan, it goes through a number of checks and then asks if you are ready to fly. With the click of a button, the drone hovers and then takes off to run its flight. You can see the images that it takes and the drone’s flight path. Our flights have been set to 75 meters height and they are supposed to be taking approximately 60-90 images for 2 hectares. Unfortunately, we have been having a lot of trouble with good flights but no images being recorded at the end. For this reason, we started using the Trial version of PIX4D and had more success.
  • Step 4 After a relatively short flight (5-12 minutes for us) the drone returns and lands and it is time to check to see if the images were collected. If it has gone well, then DroneDeploy will show you a sample mosaiced thumbnail. You need to shut down the unit and then move back to the desktop computer to upload the imagery on to their website where it is mosaiced. It took two hours for them to make the mosaic on the cloud and if you have a license you will also get a 3D model and vegetation map. For PIX4D there is a process where the images are fed from the mini-SD card to the phone and then uploaded online. You can also take the card and load them on to the PIX4D desktop app. All of these steps depend on you having the software and again I am not sure what we are going to do after the trial versions are finished.
  • Step 5. In the final step you should have several files to work with. DroneDeploy gives you the orthomosaic and a 3D digital surface model (DSF) as well as a 3D model that you view on the screen. They also provide a KML/KMZ which you can bring into Google Earth (see sample below). PIX4D provides a collection of files (including point clouds, DSFs and more) that can be downloaded. I was most interested in the orthomosaic since I can then pull that into ArcMap where I can use it for presentation and analysis (see above).

 

Conclusions

Drone mapping offers a new and dynamic way to visualize landscapes on a relatively large scale. Prices of drones have come down and the challenge is to acquire software that allows you to get your work done. Trial versions of PIX4D and DroneDeploy give you a chance to explore the possibilities and map out a few areas of interest. There are open source options that I need to explore once my trial licenses have run out. Anyone who knows my interests will realize that I am now itching to get drones into forest and mountain landscapes where they can be used to better map vegetation and land cover.

REFERENCES & FURTHER READING

Daniel, Smriti. “The Drone Buzz Over Sri Lanka.”  Sci Dev Net. 19 September 2015. Web.

Lockwood, Ian. GIS Developments at OSC in 2014.” Ian Lockwood Blog. 26 November 2014. Web. (this post features views of the OSC campus via GoogleEarth and ArcGIS).

Mason, Tony. “Put Your Drone to Work. Arc News. Summer 2016. Web.

Siddiqui, Salman. “Sri Lanka’s Drone Pioneers.” ICT Update.  18 April 2016. Web.

Written by ianlockwood

2018-05-21 at 10:23 pm

%d bloggers like this: