Geocartis measures dumpsites and landfills across India: legacy waste volume before biomining starts, stage-wise volume through the contract, and the final contour survey at completion. Outputs are the orthomosaic, digital terrain model, contours and a volume report with the base surface method declared, at 5 cm ground sample distance or better with DGPS ground control and an RMSE report. We are based in Ahmedabad and mobilise to sites nationally.
We are a survey and geospatial services company. We do not carry out biomining, and we do not sell equipment. We produce the number that the biomining contract is built on.
What CPCB actually requires
Most sectors we work in treat drone survey as an option. Legacy waste is one of the few where the guideline names it.
The CPCB Guidelines for Disposal of Legacy Waste, issued in February 2019 following NGT direction, state that a total station survey or drone mapping of any landfill or dumping site must be done before the project starts. The treatment process section is more specific still. Volume of waste is to be determined through contour survey and site measurements, and the guideline says drone mapping of heap volumes at different stages is the most cost-effective and fast method. An initial contour level survey is to be done at the start of work and a final contour level survey on completion.
The guideline also explains why volume rather than weight. Weighment of heaps is described as difficult and problematic, because payment collected on weight rewards moving the heavy fractions and leaves behind the lighter, more pollution-prone material. Paying by measured volume removes that incentive.
This sits under the Solid Waste Management Rules 2016. Rule 15(zj) requires local authorities to investigate and analyse all old open dumpsites and operational dumpsites for their biomining and bioremediation potential and to act where feasible. Rule 15(zk) permits scientific capping only where biomining and bioremediation are not possible, and Schedule I clause J puts waste reduction by biomining ahead of capping in the order of options.
The scale of the problem is in the same document. CPCB estimates more than 10,000 hectares of urban land locked in dumpsites nationally. Delhi’s dumps at Ghazipur, Bhalswa and Okhla stood at 69, 56 and 55 metres against a permissible height of up to 20 metres.
Why the volume number is the contract
Biomining is procured and paid on volume. CPCB puts on-site bioremediation cum biomining at roughly Rs 400 to Rs 700 per cubic metre, excluding capital cost and excluding the variable cost of moving screened fractions off site.
Work through what that means for a survey.
Take a dumpsite estimated at five lakh cubic metres. At Rs 500 per cubic metre that is a Rs 25 crore contract. A ten percent error in the volume estimate is Rs 2.5 crore, in one direction or the other. If the estimate is high, the urban local body over-provisions and the tender is priced against material that is not there. If it is low, the contractor runs out of contract value before the site is clear, and everybody ends up in a variation claim.
Nobody buys a drone survey for a dumpsite because the imagery is nice. They buy it because the number it produces determines the contract value, the milestone payments and, eventually, who is right in the argument.
That is also why we state the base surface method explicitly in every volume report. Volume is the difference between the waste surface and a base, and the base is a choice: the surrounding natural ground level, a surveyed hard standing, an assumed original ground profile, or a previous epoch surface. Two competent providers can produce materially different volumes from the same point cloud by choosing differently. A volume figure without a declared base is not a measurement, it is an opinion.
The shrinkage problem, and why naive progress measurement fails
This is the single most important technical point on this page, and it is where most legacy waste measurement disputes originate.
Bioremediation reduces the volume of the heap by around 35 to 40 percent before a single lorry leaves the site. That reduction comes from moisture loss and from decomposition of aerated organic matter into carbon dioxide and water vapour. The waste is being turned into windrows, exposed to air, dried and stabilised. It shrinks in place.
So if you survey a heap in January, survey it again in April, and report the difference as material processed and removed, you are wrong by a large margin. A substantial part of that difference is water and gas that left the heap. A contractor paid on the January-to-April difference gets paid for material that was never handled. An urban local body that refuses to recognise the shrinkage refuses to pay for real work.
The honest way to handle it is to separate the two effects. We survey the undisturbed heap before work starts, and that figure is the contract quantity. Through the contract we survey the working area at agreed intervals and report three things separately: material still in the original undisturbed heap, material in windrows at various stages of stabilisation, and screened fractions stockpiled on site awaiting disposal. Windrow volumes are reported as windrow volumes, not converted back to original heap equivalent, because that conversion depends on a shrinkage factor nobody has measured on your site.
Where the contract genuinely needs a shrinkage factor, it should be established from your site by measuring identified windrows through a full stabilisation cycle rather than borrowed from a guideline. We will do that measurement. We will not supply a number from a textbook and let it become the basis of a payment.
Volume, density and tonnage
Some tenders are written in tonnes rather than cubic metres. That introduces a conversion, and the conversion is the weakest link in the chain.
Legacy waste density varies enormously with age, compaction depth, moisture, soil and inert content, and how much construction debris has been dumped alongside the municipal waste. Density at the base of a 40 metre heap is not density at the top. Density in the monsoon is not density in April.
A drone survey measures volume. It cannot measure density, and any provider who converts your volume to tonnage using a single assumed figure is manufacturing precision that does not exist. Density has to come from test pits and sampling across the site and through the depth, carried out by a geotechnical or waste characterisation agency.
Our position is straightforward. We deliver volume in cubic metres, with the base surface stated. Where a tonnage figure is required, we apply the density values your characterisation study produced, show the calculation, and state the assumption in the report so that anybody reading it later can see exactly where the number came from. Where no characterisation study exists, we say so rather than filling the gap with an assumption.
How we do it
Step 1: Scoping and the base surface question
Before anything is planned we settle the site boundary, the coordinate system, the deliverables and, critically, the base surface for volume computation.
The base surface decision needs evidence. Where the dump sits on former agricultural land, the surrounding ground level gives a defensible base. Where it fills a quarry pit, an old tank bed or a low-lying area, the original ground was below the current surroundings and a surrounding-ground base will understate the volume, sometimes drastically. Old survey records, revenue maps, historical satellite imagery and test pit logs all help establish what was there. We agree the base with you in writing before the survey, because renegotiating it after the number exists is not a conversation anybody enjoys.
Below-ground waste is a category of its own. Many towns filled abandoned quarry pits, and the NGT has directed that these be biomined too. Photogrammetry measures the surface. It cannot see the depth of waste below original ground level, and that depth has to come from test pits, borehole logs or geophysical survey. We map what is above ground and are explicit about where the measured volume stops.
Step 2: Airspace and permissions
Dumpsites are usually on the edge of a city, which puts a fair number of them inside the yellow zone around an airport. We check the site on the Digital Sky airspace map before quoting. Green zone sites can be flown to 120 metres above ground level without prior flight permission, yellow zone sites need permission and a lower ceiling, red zone sites cannot be flown.
Site permission comes from the urban local body or the concessionaire operating the site, and on an operating landfill the site manager needs to be part of the plan rather than informed on the day.
Our aircraft carry active Unique Identification Numbers and our pilots hold DGCA Remote Pilot Certificates.
Step 3: Ground control
Control points go in on stable ground around the perimeter and, where safe, on the heap itself. Perimeter-only control on a tall dump leaves the top of the heap poorly constrained, and the top of the heap is where the volume is.
Points are surveyed with a calibrated DGPS and marked as high-contrast crosses. On sites that will be surveyed repeatedly through a two or three year biomining contract, we establish permanent control on undisturbed ground outside the working area, chosen so it survives the entire programme. Every subsequent survey ties to the same frame, which is what makes the epoch-to-epoch differences defensible.
Independent checkpoints go in as well, withheld from the bundle adjustment, and they are how we measure accuracy rather than assert it.
Step 4: Flight planning over a tall heap
Ground sample distance is pixel pitch multiplied by flying height divided by focal length. A 20 megapixel one-inch sensor with 5472 pixels across 13.2 millimetres has a pixel pitch of about 2.41 micrometres. With an 8.8 millimetre lens at the 120 metre ceiling that gives roughly 3.3 centimetres GSD.
Tall dumps compress that margin in a way flat sites do not. A 40 metre heap flown at 120 metres above the take-off point leaves only 80 metres above the crest, so GSD at the top is around 2.2 centimetres while GSD at the toe is 3.3. That variation is manageable. On a genuinely large dump the arithmetic gets tighter, and terrain-following planning against a previous survey or a coarse elevation model keeps resolution consistent across the whole site.
Slope faces are the other planning problem. A dump has steep flanks, and nadir imagery reconstructs a steep face poorly because it is barely visible from directly above. Every dumpsite survey we fly includes oblique passes around the perimeter, angled into the slopes, in addition to the nadir block. Skipping those produces a surface that looks complete and systematically misrepresents the flanks, which on a conical heap is a large share of the volume.
Step 5: Capture on an operating dumpsite
Dumpsites are the least pleasant sites we work on and the ones with the most operational hazards.
Fire. Most large dumps are smouldering somewhere. Hidden fires produce smoke plumes that obscure the ground, degrade image quality across whole strips, and add heat and turbulence. We plan capture around known smoking points and reschedule strips where smoke is moving across the block rather than flying through it and delivering a compromised surface.
Methane and landfill gas. Airless rotting waste generates methane, which is flammable. Nothing about a normal survey ignites it, and it is a reason the crew works to the site’s safety rules rather than its own.
Slope instability. CPCB warns that leaving a vertical wall of waste during operations can cause a dangerous landslide, and recommends working downward from the top with a safe slope of 25 to 30 degrees. Our crews do not walk on active faces to place control. Where a control point on the heap is needed and the face is not safe, it does not go in and we say so.
Leachate. Ponds and channels around the toe are not walkable. They also produce no reliable tie points in the imagery and appear as noise or holes in the cloud, so their extent gets mapped as a polygon and excluded from the volume boundary rather than interpolated across.
Birds. Large dumps carry large raptor and kite populations, and they take an interest in drones. It is a real operational constraint and it affects when we fly.
Step 6: Processing and classification
Aerial triangulation with bundle adjustment against the surveyed control and camera self-calibration. Dense matching to generate the point cloud. Then classification, which on a dumpsite is harder than it looks.
The classifier has to separate the waste surface from vegetation growing on the heap, from plant and vehicles working on it, from site buildings and from the windrows and screened stockpiles that are part of the process rather than part of the remaining heap. Scrub growing on an old stabilised flank reads as ground to most automatic filters and sits half a metre above it. Screened fine stockpiles have the same geometry as untouched waste. These get separated by hand against the site plan and against what the operator tells us is where.
The output is a set of surfaces rather than one: remaining undisturbed waste, windrows by stage, screened fractions by type, and the recovered ground where clearance is complete.
Step 7: Volume computation and reporting
Volumes are computed for each of those surfaces separately against the agreed base, and reported with the method stated. The report says what was measured, what base was used, what was excluded and why, and what the checkpoint residuals were.
Where the survey is one epoch in a series, we also report the difference against the previous epoch, with the shrinkage caveat set out explicitly rather than buried.
Step 8: Quality control and delivery
Residuals at withheld checkpoints, RMSE reported horizontally and vertically. Deliverables issued with projection metadata embedded in every spatial file, organised by epoch where the survey is recurring.
Accuracy and what it means for a volume
Ground sample distance and accuracy are different quantities. GSD is the ground area one pixel covers. Accuracy is how close a coordinate is to the truth.
For a well-controlled photogrammetric block, horizontal RMSE typically lands between one and two times the GSD and vertical between two and three times. At 5 cm GSD that suggests roughly 5 to 10 centimetres horizontal and 10 to 15 centimetres vertical. Your figures come from your checkpoints.
Vertical accuracy is what matters here, because volume is area multiplied by height difference. A systematic 15 centimetre vertical bias across a 10 hectare dumpsite is 15,000 cubic metres of apparent material, which at Rs 500 per cubic metre is Rs 75 lakh. That is the argument for proper control, for oblique coverage of the flanks, and for reporting the measured vertical RMSE rather than a marketing figure.
Random error behaves differently from systematic error in volume computation, and it is worth understanding the difference. Random noise across a large surface largely cancels when you integrate it into a volume. A systematic bias does not cancel at all, it multiplies by the area. This is why we care more about control geometry and camera calibration than about squeezing the last millimetre of GSD.
Two site conditions degrade results. Dense vegetation on old flanks prevents the ground being seen, so the surface there is the top of the scrub unless it is classified out, and classification under thick growth is interpolation. Standing water and leachate produce no reliable matching and are excluded rather than guessed.
Deliverables and output file formats
| Deliverable | What it is | Format |
|---|---|---|
| Orthomosaic | Georeferenced image of the site and immediate surroundings | TIFF (GeoTIFF), JPEG |
| Digital terrain model | Waste surface and recovered ground, gridded | TIFF |
| Digital surface model | Everything captured, including vegetation, plant and buildings | TIFF |
| Contour survey | The initial and final contour surveys CPCB requires, at your specified interval | DXF, SHP, PDF |
| 3D point cloud | Classified, RGB attributed | LAS, LAZ |
| Volume report | Waste volume in cubic metres against the declared base surface, by zone, with method and exclusions stated | PDF, XLSX |
| Zone and feature polygons | Waste footprint, windrow areas, screened stockpiles, leachate ponds, recovered ground, site infrastructure, with areas computed | SHP, DXF |
| Cross sections | Through the heap at specified lines, for depth profile and slope geometry | DXF, DWG, PDF |
| Slope analysis | Slope angle raster for stability assessment against the 25 to 30 degree working guidance | TIFF, PDF |
| Object marking | Site boundary, access roads, drains, buildings, weighbridge, processing plant, gas and leachate infrastructure | DXF, TIFF |
| Change detection surface | Difference between two epochs, cut and fill mapped as raster | TIFF, PDF |
| Thermal orthomosaic | Surface hotspot mapping for subsurface fire detection | TIFF, JPEG |
| Progress photo and video set | Dated, georeferenced record of the site and work fronts | JPEG, MP4 |
| RMSE and quality report | Residuals, control layout, processing parameters, software | |
| Flight log and survey record | Flights, heights, times, drone UIN, pilot licence number |
Raw imagery is handed over with the deliverables. On a contract where the volume figure may be disputed years later, holding the raw data yourself matters.
The survey programme across a biomining contract
CPCB requires an initial contour survey at the start and a final contour survey at completion. In practice a contract that only does those two is measuring nothing for two years and then arguing about the gap.
What works is a programme.
Pre-tender survey. The undisturbed heap, before anything is procured. This produces the quantity the tender is written against, and it is the survey that protects the urban local body from tendering a number pulled from a decade-old estimate.
Baseline at contract start. Repeat capture at award, tied to permanent control, establishing the agreed starting surface both parties sign off. Where the pre-tender survey is recent and the site undisturbed, this can be the same dataset.
Stage surveys. Monthly or quarterly depending on contract size, reporting remaining heap, windrows by stage and screened stockpiles separately. This is what supports milestone payments and catches problems while they are still fixable.
Final contour survey. At completion, establishing recovered ground level and the residual left on site. CPCB expects residual rejects at under ten percent of the original waste.
Post-closure surveys. Periodic capture after handover. Cleared sites are not permitted for habitation for at least 15 years under Schedule I, and CPCB recommends a buffer of up to 500 metres around a cleared site declared free of new habitation. A dated aerial record is how a local body demonstrates that the recovered land has not quietly been built on.
For an urban local body, this converts a one-off survey purchase into a defined programme with a known cost across the contract. For a biomining contractor, it converts a payment argument into a measurement.
Operating landfills and processing sites
Not every solid waste survey is legacy waste.
Active landfill cells. Remaining airspace measurement, fill rate against permitted capacity, cell geometry, daily cover verification and slope monitoring. Airspace is the asset an operating landfill sells, and measuring it monthly is the difference between managing capacity and discovering you have run out.
Processing facilities. Compost windrow volumes, RDF and inert stockpiles at material recovery facilities, and layout mapping for capacity expansion.
Construction and demolition waste sites. Stockpile volumes by fraction, and yard layout.
Closure and capping projects. Where biomining is genuinely not feasible and capping is being done under Rule 15(zk), the survey supports the capping design, the volume of cover material and the verification that the profile was built as designed.
New site selection. Terrain, drainage, catchment and buffer distance mapping for proposed processing or disposal sites.
Where we work
We are based in Ahmedabad and mobilise nationally. Legacy waste work follows municipal programmes rather than industrial belts, so it is spread across almost every state.
Gujarat. Ahmedabad, where Pirana is the best-known site in the state, plus Surat, Vadodara, Rajkot, Bhavnagar, Jamnagar, Junagadh, Gandhinagar, Anand, Nadiad, Mehsana and Bhuj. Vadodara was among the cities CPCB recorded as having biomining under way when the guidelines were issued.
Maharashtra. Mumbai, Navi Mumbai, Thane, Pune, Nashik, Nagpur, Chhatrapati Sambhajinagar, Solapur and Kolhapur.
Northern India. Delhi NCR including Ghaziabad, Noida, Gurugram and Faridabad, plus Jaipur, Jodhpur, Udaipur, Kota, Ludhiana, Amritsar, Chandigarh, Dehradun, Lucknow, Kanpur, Varanasi, Prayagraj, Agra and Patna.
Central India. Indore, whose Devguradia site is the most cited success in the country, plus Bhopal, Jabalpur, Gwalior, Ujjain, Raipur and Bilaspur.
Eastern India. Kolkata, Howrah, Bhubaneswar, Cuttack, Rourkela, Ranchi, Jamshedpur, Dhanbad, Guwahati and the north-eastern state capitals.
Southern India. Hyderabad, Bengaluru, Chennai, Coimbatore, Madurai, Tiruchirappalli, Vijayawada, Visakhapatnam, Kochi, Thiruvananthapuram, Mysuru and Mangaluru.
What we do not do
We do not carry out biomining or bioremediation. We measure sites for the people who do, and we are not bidding against our own clients.
We do not determine waste density or composition. That needs test pits, sampling and NABL laboratory analysis, and it is a separate scope.
We do not measure below-ground waste depth. Photogrammetry sees the surface. Depth in a filled quarry pit or tank bed comes from boreholes, test pits or geophysical survey.
We do not carry out the heavy metal, leachate and groundwater baseline testing that CPCB requires before and after biomining. That is NABL laboratory work.
We do not walk unstable waste faces to place control. Where a point cannot be established safely it does not go in, and the report states that the area is less well constrained as a result.
Frequently asked questions
Does CPCB require a drone survey of a dumpsite? The CPCB Guidelines for Disposal of Legacy Waste state that a total station survey or drone mapping must be done before the project starts, that volume is to be determined through contour survey and site measurements, and that drone mapping of heap volumes at different stages is the most cost-effective and fast method. An initial contour survey at start of work and a final contour survey at completion are both specified.
Why is volume used rather than weight? CPCB describes weighment of heaps as difficult and problematic, because paying by weight rewards removing the heavy fractions and leaving behind the lighter, more pollution-prone material. Volume avoids that.
How accurate is the volume figure? Accuracy depends on control quality, coverage of the slopes, and the base surface. With proper control and oblique coverage of the flanks, vertical RMSE at 5 cm GSD is typically in the 10 to 15 centimetre range, and the volume uncertainty follows from that across the site area. We report the measured residuals and state the base surface, so you can see the basis of the number rather than being asked to trust it.
Why did the heap shrink when we have not removed much material? Bioremediation reduces waste volume by around 35 to 40 percent through moisture loss and decomposition, before any material leaves site. Progress measurement that treats the whole reduction as material processed will overstate the work done. We report remaining heap, windrows and screened stockpiles separately for exactly this reason.
Can you give us tonnage rather than cubic metres? Only by applying a density figure from your waste characterisation study, with the calculation and the assumption stated in the report. A drone survey measures volume. Density varies too much across and through a dumpsite to be assumed.
Can you survey a site that is on fire? Partially. Smoke obscures the ground and degrades imagery, so we plan around active smoking points and reschedule affected strips. A thermal survey to map surface hotspots is a useful separate deliverable and is often worth flying at the same time.
Can you survey while biomining is in progress? Yes, and it is the normal case. We coordinate with the site operator, and the classification separates undisturbed heap, windrows and screened stockpiles so the report reflects what is actually where.
What file formats do you deliver? Orthomosaic as GeoTIFF and JPEG. DTM and DSM as GeoTIFF. Contours as DXF, SHP and PDF. Zone polygons as SHP. Cross sections as DXF, DWG and PDF. Point cloud as LAS and LAZ. Object marking as DXF and TIFF. Volume reports as PDF and XLSX.
How long does a dumpsite survey take? Capture on a typical municipal site is a single day, including the oblique passes. Ground control establishment may be a separate earlier visit. Processing and reporting follow, and the delivery date is agreed at proposal stage.
Can you compare this survey against one done by somebody else? Sometimes. It depends on whether their control was properly recorded and whether their base surface is known. Where either is missing, the two datasets can be overlaid but the volume difference between them cannot be relied on, and we will tell you that rather than producing a comparison that looks authoritative and is not.
Get a quote for your site
Send us the site boundary as a KML or shapefile, the approximate area, the approximate height of the heap, whether the site is active or closed, and whether you need a pre-tender quantity, a contract baseline, stage measurement or a final contour survey. Tell us if a waste characterisation study exists, and if there is any record of what the original ground level was.
We will come back with the control plan, the flight plan, the base surface we propose and why, a delivery schedule and a fixed price.