Geocartis works in the aviation sector across India. Most of that work is survey rather than aircraft inspection: site coordinates and elevation certification for AAI height clearance applications, obstacle and approach path survey, airport landside and terminal construction monitoring, and hangar and MRO facility survey. Aircraft exterior inspection by drone is a real and established technique, and in India it sits inside a regulatory system that this page explains honestly before offering anything.
We are a survey and inspection services company. We do not build drones, we are not an approved maintenance organisation, and we hold no aviation maintenance approvals.
Read this first: aircraft inspection in India has three barriers
Drone-based aircraft exterior inspection is genuine technology. Internationally it is used for lightning strike inspection, hail damage assessment and general visual inspection of airframes, and the time saving is dramatic. A lightning strike inspection that conventionally means a maintenance engineer working over the airframe from cherry pickers for the better part of a shift can be captured by a drone in a fraction of that. On an aircraft on ground, where every hour has a cost, that is a serious proposition.
In India, three things stand between that technology and a third-party survey company.
Airspace. Airports are among the most restricted airspace in the country. Outdoor operation on an apron, a taxiway or anywhere airside is not something a commercial drone operator does. Whatever aircraft inspection happens, happens inside a hangar.
Indoor flight. A hangar has no GNSS. Flying inside one requires an aircraft designed for GNSS-denied operation with onboard positioning, typically laser or vision based, and it requires a pilot trained on that platform. It is a different machine from a survey drone and a different skill. We are open about not currently offering it.
The maintenance regulatory system. This is the fundamental one. Aircraft maintenance in India is carried out by DGCA-approved maintenance organisations, by licensed and authorised personnel, under approved maintenance programmes and approved procedures. An inspection that forms part of maintenance and leads to a release to service must sit inside that system. A third party cannot simply arrive at a hangar and inspect an aircraft, and the findings from any inspection method have to be assessed and certified by licensed engineers, not by a survey company.
Where drone inspection is used seriously in aviation, the system is adopted by the maintenance organisation, written into its approved procedures, and operated within its quality system, often against a procedure the airframe manufacturer has published. It is an MRO capability, not a service somebody sells into an MRO from outside.
So our honest position. If you are an MRO or an operator who has, or is developing, an approved drone inspection procedure and needs a survey and data partner rather than a maintenance provider, we are willing to have that conversation and to say clearly what we can and cannot contribute. If you are looking for a company to come and inspect your aircraft, we are not it, and we would be cautious of anybody in India who says they are without being able to show you where they sit in the approval chain.
The rest of this page is about the aviation work we can actually do, and there is a good deal of it.
AAI height clearance surveys, and why applications get rejected
This is the largest and most immediate aviation-related survey market in India, and it has nothing to do with aircraft.
Any structure above a certain height within a defined distance of an airport requires a no objection certificate for height clearance from the Airports Authority of India, applied for through the NOCAS portal, under the rules notified in G.S.R. 751(E). The distances are measured from the Aerodrome Reference Point of the nearest airport, and run up to 20 kilometres for visual flight rules airports and up to 56 kilometres for instrument flight rules airports. Beyond those distances, a structure below 150 metres above ground level does not need an AAI NOC.
AAI has published Colour Coded Zoning Maps for a large number of airports, which give a Permissible Top Elevation for each grid in each coloured zone. Where the requested top elevation is below the permissible top elevation, a local body can approve the building without referring to AAI. Permitted structure height is the CCZM permissible top elevation minus the site elevation, and the maximum elevation approvable through the CCZM route is 150 metres, above which the application goes to NOCAS.
Here is the survey part. The applicant has to submit a certificate of site elevation and site coordinates, in AAI’s prescribed format, from Survey of India or from a licensed or empanelled surveyor, along with photographs of the site and neighbouring areas taken by a surveyor and the site plotted on Google Earth. Corner coordinates of the plot are required, not just a mid-point; a single mid-point is accepted only for masts, chimneys, transmission lines and buildings on plots up to 300 square metres. Where there are multiple buildings on a plot, corner coordinates are needed for each. An approved NOC is valid for eight years.
And here is the commercial argument. A large share of NOC applications are rejected, and AAI has published a list of common reasons. They are overwhelmingly documentation failures rather than genuine obstruction problems: wrong format, incomplete owner information, and, repeatedly, mismatch between the site coordinates stated in the application and those on the site elevation certificate.
Those are survey and documentation errors. A rejected application on a project with a construction programme attached is weeks or months lost, and it is entirely avoidable.
What we produce: corner coordinates of the plot and of each proposed building in WGS-84, site elevation above mean sea level, the certificate in AAI’s prescribed format, the site and surroundings photography, the Google Earth plot, and the check of your requested top elevation against the CCZM permissible top elevation for your grid, so you know before you apply whether you need to go to AAI at all.
The elevation problem nobody warns applicants about
This is the technical heart of NOC survey work and it is where inexperienced providers produce certificates that are wrong by tens of metres.
A GNSS receiver does not natively measure height above mean sea level. It measures height above the WGS-84 reference ellipsoid, which is a mathematical surface, not the sea. The difference between the two, the geoid undulation, varies across India and is not small. Reporting an ellipsoidal height where an orthometric height above mean sea level is required is not a rounding error; it is a systematic error of a magnitude that would render a height clearance certificate meaningless.
Converting correctly requires either a validated geoid model applied properly, or a tie to an established benchmark of known reduced level, or both. On any NOC survey we state which method was used and what the reduction was, so an assessor can see the basis of the figure rather than being asked to trust it.
The same care applies to the horizontal. AAI works in WGS-84, and a coordinate transformed carelessly from a local grid or a project datum will not match. Given that coordinate mismatch is one of AAI’s own listed rejection reasons, this is not a theoretical concern.
If you are commissioning an NOC survey from anybody, ask two questions. How was mean sea level elevation derived from the GNSS observation, and what geoid model or benchmark was used. A provider who cannot answer clearly should not be preparing your certificate.
Other aviation survey work
Obstacle and approach path survey. Existing structures, terrain, trees, masts and cranes within an approach or transitional surface, measured with heights above mean sea level. Useful for airport operators assessing obstacle environments, for developers checking a site before committing, and for anybody contesting or supporting an objection.
Construction cranes near airports. Tower cranes need their own height clearance, and a crane’s maximum height including jib is what matters. Survey of the crane position and the base elevation supports the application, and repeat capture confirms the erected height matches what was cleared.
Airport landside and terminal construction monitoring. Terminal buildings, car parks, access roads, cargo facilities, hotels and the wider airport city are ordinary construction projects, and the landside area is often outside the restricted airside boundary. Baseline survey, earthwork quantities, monthly progress and as-built comparison all apply, as set out on our construction survey page. The airspace position needs checking case by case and it will not always be favourable.
Hangar and MRO facility construction. New hangars, maintenance facilities, component shops and their aprons are large industrial buildings with the same survey requirements as any other. This is the most realistic route into the aviation maintenance sector for a survey company: build the facility rather than inspect the aircraft.
Airport land, perimeter and encroachment. Boundary condition, perimeter road and fence, encroachment onto airport land, and land parcels held for expansion. Airport operators hold substantial land and it is subject to the same pressures as railway land.
Airstrips, helipads and general aviation. Private airstrips, industrial and hospital helipads, and general aviation facilities away from major airports sit in a much less restricted environment than a commercial airport, and surface, approach and obstacle survey is straightforward there.
Post-event documentation. After a cyclone, flood or fire affecting airport landside infrastructure, dated georeferenced capture for insurance and reinstatement.
How we do it
Step 1: Establish the regulatory position first
On any aviation enquiry the first exercise is not a quotation. It is establishing where the site sits: distance from the nearest Aerodrome Reference Point, whether the airport is VFR or IFR, whether a Colour Coded Zoning Map exists for it, and what the DGCA airspace classification is for the survey itself.
Those answers determine whether an NOC is needed at all, whether the CCZM route is available, and whether we can fly. On a fair number of sites near an airport, drone flying is restricted or prohibited, which does not prevent us doing the survey; it means the survey is done by ground methods with GNSS and levelling rather than from the air. We will say when that is the case. An NOC survey does not require a drone, and the deliverable is a certificate rather than an orthomosaic.
Step 2: Control and reduction to mean sea level
Observations are made with survey-grade GNSS, tied to a benchmark of established reduced level where one is reachable, and reduced to mean sea level with the geoid model and method stated.
Corner coordinates are observed at the actual plot corners and at the corners of each proposed building, not derived from a plan. Where a corner is inaccessible, that is recorded and the method used to establish it is stated.
Where the survey is aerial, control is established and the RMSE reported as on any other survey.
Step 3: The site record
AAI requires photographs of the site and the neighbouring areas taken by the surveyor, and the site plotted on Google Earth. We produce both, dated, with the photograph positions recorded so the imagery is verifiable rather than generic.
Where drone capture is permitted, an orthomosaic of the site and surroundings makes a materially better submission record than ground photographs, and it also shows the existing built heights around the plot, which is useful context when a requested height is being argued.
Step 4: The CCZM check
Before you apply, we establish which coloured zone and grid your plot falls in, the permissible top elevation for it, and therefore the permitted structure height at your measured site elevation. That tells you whether your proposed height clears without an AAI application, whether it needs one, and if it needs one, how far above the permissible elevation you are asking to go.
Doing that check first is the difference between an informed application and a speculative one.
Step 5: Certificate and submission pack
The certificate is issued in AAI’s prescribed format with the coordinates, elevation, method and datum stated. The pack includes the coordinate schedule, the elevation derivation, the photographs, the Google Earth plot and the CCZM assessment.
We prepare the survey and documentation. The application itself is filed by the applicant on NOCAS, and we will assist with assembling what it needs.
Accuracy
For GNSS observations of plot corners and elevation, accuracy is a function of observation method, duration, baseline length and the geoid reduction, and the achieved figures are stated on the certificate.
For aerial survey work, the usual photogrammetric relationship applies: horizontal RMSE typically one to two times the ground sample distance and vertical two to three times, measured against withheld checkpoints.
On an NOC survey the vertical is what matters and the error that matters is systematic rather than random. A few centimetres of random noise on a site elevation is irrelevant to a height clearance decision. A wrongly applied geoid separation is not. That is why the method is stated rather than just the number.
Deliverables and output file formats
| Deliverable | What it is | Format |
|---|---|---|
| Site elevation and coordinates certificate | AAI prescribed format, corner coordinates in WGS-84 and site elevation above mean sea level, with method and datum stated | |
| Coordinate schedule | All plot and building corner coordinates, tabulated | XLSX, PDF, DWG |
| Elevation derivation note | Observation method, benchmark or geoid model used, and the reduction applied | |
| CCZM assessment | Zone and grid identified, permissible top elevation, and permitted structure height at your site elevation | |
| Site and surroundings photography | Dated surveyor photographs with positions recorded | JPEG, PDF |
| Google Earth plot | Site plotted for submission | KML, PDF |
| Site orthomosaic | Where aerial capture is permitted, georeferenced imagery of the plot and surroundings | TIFF (GeoTIFF), JPEG |
| Obstacle survey | Existing structures, trees and terrain with heights above mean sea level within a defined area | SHP, DWG, XLSX, PDF |
| Crane height clearance survey | Crane position, base elevation and maximum height including jib | PDF, DWG |
| Construction progress outputs | Earthwork quantities, progress by block, as-built comparison for landside works | PDF, XLSX, TIFF, DWG |
| Airport land and encroachment layer | Boundary against occupation, dated and attributed | SHP, DXF, PDF |
| Survey report | Method, control, accuracy, datum, findings and limitations | |
| Flight log and survey record | Where aerial capture was used: flights, heights, times, drone UIN, pilot licence number |
Where we work
We are based in Ahmedabad and work nationally, with NOC survey work concentrated where development pressure near airports is highest.
Gujarat. Ahmedabad, where Sardar Vallabhbhai Patel International Airport sits inside the built-up area and a very large part of the city therefore falls within the distance at which height clearance becomes a question, plus Surat, Vadodara, Rajkot, Bhavnagar, Jamnagar, Bhuj, Kandla, Porbandar and the Dholera airport area.
Western India. Mumbai and Navi Mumbai, Pune, Nashik, Nagpur, Goa and Chhatrapati Sambhajinagar.
Northern India. Delhi NCR including Noida and the Jewar airport area, Jaipur, Chandigarh, Amritsar, Lucknow, Kanpur, Varanasi, Dehradun and Patna.
Central India. Indore, Bhopal, Raipur and Jabalpur.
Southern India. Hyderabad, Bengaluru, Chennai, Coimbatore, Kochi, Thiruvananthapuram, Visakhapatnam and Mangaluru.
Eastern India. Kolkata, Bhubaneswar, Ranchi and Guwahati.
Height clearance work is concentrated in cities with an airport near the centre and active high-rise development, which describes most of the above.
What we do not do
We do not inspect aircraft. We hold no aviation maintenance approvals and we are not an approved maintenance organisation.
We do not fly airside at any airport.
We do not fly inside hangars, which requires a GNSS-denied platform we do not operate.
We do not issue no objection certificates. AAI issues those. We prepare the survey and documentation that an application requires.
We do not guarantee that an application will be approved. Approval depends on the obstacle environment and AAI’s assessment, and a correctly prepared application can still be refused on genuine height grounds.
We do not file the NOCAS application on your behalf as the applicant, though we will help assemble what it needs.
We do not certify structural or aeronautical matters, and we are not aviation consultants.
We do not fly in red zones.
Frequently asked questions
Can you inspect our aircraft with a drone? No. Aircraft maintenance in India sits within the DGCA approval system, inspection forming part of maintenance must be carried out under an approved organisation by authorised personnel, airports are restricted airspace, and hangar flying needs a GNSS-denied platform we do not operate. If you are an MRO developing your own approved capability and want a survey and data partner, that is a different conversation and we are open to it.
Do we need an AAI height clearance NOC? It depends on your distance from the nearest Aerodrome Reference Point, whether that airport is VFR or IFR, your proposed top elevation, and whether a Colour Coded Zoning Map covers it. Beyond 20 kilometres from a VFR airport or 56 kilometres from an IFR airport, a structure below 150 metres above ground level does not need one. Within those distances, the CCZM tells you whether your local body can approve it or whether AAI must. We establish the position before you apply.
Why do so many NOC applications get rejected? AAI publishes the common reasons, and they are mostly documentation failures rather than genuine obstruction: wrong format, incomplete information, and mismatch between the coordinates in the application and those on the site elevation certificate. Those are avoidable with a properly prepared survey.
Can you give us the site elevation from a phone or a handheld GPS? No, and neither should anyone else. A GNSS receiver measures height above the WGS-84 ellipsoid, not above mean sea level, and the difference across India is tens of metres. The conversion needs a validated geoid model or a tie to an established benchmark, and the certificate should state which was used.
Do you need to fly a drone to do an NOC survey? No. The deliverable is a certificate of coordinates and elevation, which is GNSS and levelling work. Aerial capture adds a good site record where the airspace permits it, and near an airport it frequently does not. We will tell you which applies.
Can you survey for a tower crane clearance? Yes. Crane position, base elevation and maximum height including the jib, in the form the application needs.
Can you monitor construction of an airport terminal? Landside, generally yes, subject to the airspace position for the specific site, which needs checking case by case and will not always be favourable. Airside, no.
How long does the survey take? The site work is usually short. The longer items are assembling the documentation correctly and, after that, AAI’s own processing, which is outside anybody’s control. Start early relative to your construction programme.
Is the NOC permanent? An approved NOC is valid for eight years. Revalidation is applied for through NOCAS.
What file formats do you deliver? Certificate, derivation note and reports as PDF. Coordinate schedules as XLSX and DWG. Google Earth plot as KML. Aerial outputs, where captured, as GeoTIFF and DWG.
Get in touch
Tell us the site location, the plot boundary, your proposed top height, and the nearest airport. We will establish whether an NOC is required, whether the CCZM route is available, and what the survey needs to produce.
If you are an MRO or operator with an approved inspection procedure looking for a survey partner, tell us what you have in place and we will tell you honestly whether we can contribute.