TL;DR: Stockpile reconciliation software helps a quarry or mine prove its month-end stock number: what was measured, when, at what density, and how it ties to production and sales. Measurement tools produce the survey number, and quarry management systems hold the sales side. Choose on how complete the trail is from survey to the figure finance signs.
Key takeaways
- Auditors expect to see stock counted. According to the PCAOB's auditing standard on inventories, observation of inventories is a generally accepted auditing procedure.
- Drones are already part of audits. According to a 2023 PCAOB briefing paper, audit firms tell audit committees where new technologies such as drones are used to observe inventory.
- Tonnage carries a second error. According to the help center of Birdi (birdi.io), a density of 1.6 against 1.8 t/m³ is a 12% swing in tons on the same volume.
- The stakes are high per ton. According to the US Geological Survey, US crushed stone averaged $18.50 a ton in 2025.
- A trail matters as much as a number. Dated surveys, saved densities and exported results are what let someone check the figure months later.
What does stockpile reconciliation software need to do?
Stockpile reconciliation software needs to produce a closing stock figure that ties to opening stock, production and sales, and to show how that figure was made. That means a dated measurement, a recorded density, the base surface used, and an export finance can use. Book stock comes from quarry management systems; the measured figure comes from a survey.
Reconciliation compares the two. Book stock is opening stock plus production minus sales. Survey stock is what is actually on the ground. The gap between them, sometimes called the stock adjustment, is what finance books and what auditors question. A small, steady gap is normal; a growing one means something is being lost or mismeasured.
Why the trail matters
At month end, the number gets used. At year end, someone asks how it was made. So the software should keep each survey dated, each density recorded, and each result exported, so the figure can be rebuilt later. For the routine itself, see our guide to reconciling stockpile volumes.
How did we choose and compare the tools?
We chose tools that quarries and mines use to measure and reconcile stockpile inventory, and compared them on how stock is measured, tonnage and density control, export to finance, the audit trail, access for people outside the paid team, and pricing. Birdi is listed first, and the order is not a ranking.
Every fact was checked on the vendor's own website or help center on October 7, 2026. We say plainly where a tool does not produce a report some buyers expect, such as a royalty or levy return, including for Birdi. Those returns are usually prepared by the business from the measured figures.
The best stockpile inventory and reconciliation software in 2026
The stockpile inventory and reconciliation tools compared here are Birdi, Stockpile Reports, Propeller, DroneDeploy and QuarryLink. Four measure stock from survey or phone data, and one is a quarry management system that holds the sales and book stock side. Each entry carries the same fields, checked on October 7, 2026.
1. Birdi
Best for: Quarries and mines that want month-end volumes, tonnage and the change since last survey in one record that site, finance and auditors can open.
Typical customer size / segment: Mid-sized quarry, mining and construction teams of roughly 30 to 500 staff.
Key strengths:
- A material library and custom densities saved to the workspace, so the whole team uses one density per material; tonnage appears in table view and PDF exports on Growth and Ultimate.
- The Base DEM method reads material added or removed since an earlier survey.
- Table view exports to CSV, and annotation reports export as PDF.
Audit trail: Dated surveys grouped by site, with densities and results exported each month. Recalculating overwrites a result, so export after each survey.
Access for people outside the paid team: Guests view and download without using a paid seat.
Data types in one view: Orthomosaics, elevation models, point clouds and documents.
Processing: Cloud.
Watch-outs: Not for a surveyor who wants hands-on control of photogrammetry processing. It also does not suit a sole operator shopping on price.
Pricing: Growth is $287 USD a month, billed annually. Ultimate is priced by quote (checked October 7, 2026).
2. Stockpile Reports
Best for: Aggregates producers with many sites that want frequent phone, drone or camera measurements in one inventory system.
Typical customer size / segment: From single yards to organizations with more than 200 stockpiles across several countries.
Key strengths:
- Each report is a timestamped measurement with volume, tonnage, site and product.
- A coverage confidence score on every measurement computed from imagery.
- Measurements queryable from AI assistants, grounded in your own data.
Audit trail: Timestamped, structured reports per pile.
Access for people outside the paid team: Business plans include unlimited users.
Data types in one view: Stockpile measurements and reports by product and site.
Processing: Cloud.
Watch-outs: It is built around stockpiles, so other site survey data lives elsewhere.
Pricing: Business plans from $100 a month for up to 10 piles; larger accounts by quote (checked October 7, 2026).
3. Propeller
Best for: Survey-led quarries and mines that reconcile volumes frequently against haul fleet data.
Typical customer size / segment: Mining, quarry and earthworks operators whose survey team owns the workflow.
Key strengths:
- Daily reconciliation, as described on its mining page.
- Material properties for mass and value.
- DirtMate machine data for load counts between surveys.
Audit trail: Survey history per site.
Access for people outside the paid team: View-only permission by default for new users.
Data types in one view: Surveys, point clouds, design surfaces and machine data.
Processing: Cloud, with its own ground control hardware.
Watch-outs: Pricing is by quote. The platform centers on the survey team, so plan how finance will use it.
Pricing: Contact for pricing.
4. DroneDeploy
Best for: Organizations that want stockpile reports inside a wider drone platform used across many sites.
Typical customer size / segment: Individual pilots through to enterprise teams.
Key strengths:
- Stockpile reports and volume tools.
- A compare tool for two map dates side by side.
- Integrations with Esri, Autodesk and Procore.
Audit trail: Map history by date.
Access for people outside the paid team: View-only links to a single map date on paid accounts.
Data types in one view: Orthomosaics, elevation, 3D models and video.
Processing: Cloud.
Watch-outs: Stakeholders who want to use the tools need a paid account, and team plans are by quote.
Pricing: Flight & Analysis is $4,188 USD billed annually for one pilot; team plans by quote (checked October 7, 2026).
5. QuarryLink
Best for: Quarries that need the sales, weighbridge and book stock side of reconciliation in one system.
Typical customer size / segment: Quarries and aggregates producers, particularly in Australia.
Key strengths:
- Production, weighbridge, stockpile, jobs and invoicing in one platform.
- Automated weight capture and load verification at the weighbridge.
- Reporting across the quarry operation.
Audit trail: Weighbridge and sales records.
Access for people outside the paid team: Through the system's own users and reports.
Data types in one view: Sales, dispatch, production and stock records.
Processing: Hosted.
Watch-outs: It does not measure what is on the ground, so it needs a survey figure to reconcile against.
Pricing: Contact for pricing.
What do auditors ask about stockpile numbers?
Auditors ask how the stock was measured, when, by whom, at what density, and how the figure ties to the books. Under the PCAOB's standard, observing inventory is a generally accepted auditing procedure, so expect an auditor to want to see the count, or evidence of it. Drone surveys are increasingly part of that evidence.
The questions to prepare for
- What method measured the stock, and when? The survey date and method.
- What base surface was used under each pile? Different bases give different volumes.
- What density converted volume to tons, and where did it come from? A tested density beats a library default.
- Who checked the result? A named person who signed off the figure.
- How does it reconcile to production and sales? The stock adjustment and its explanation.
The 2023 PCAOB briefing paper notes that audit firms tell audit committees where technologies such as drones are used to observe inventory. So a dated drone survey, with its density and base recorded, is a reasonable thing to hand an auditor.
Why does survey stock differ from book stock?
Survey stock differs from book stock because they measure different things in different ways. Book stock is calculated from production and sales records, which miss spillage, internal transfers and moisture changes. Survey stock measures the volume on the ground and converts it with a density that changes with moisture and compaction. A small, steady difference is normal.
Watch the trend rather than one month. A gap that grows month after month points to a measurement problem, a density that no longer fits the material, or real loss. Measuring more often makes that trend visible sooner. For more on how density and ground control affect the number, see our guide to ground control and volumes.
Frequently asked questions
How do you reconcile stockpile inventory?
Start with opening stock, add production and subtract sales to get book stock. Measure the stockpiles to get survey stock, converting volume to tons with a tested density. The difference is the stock adjustment. Record the survey date, method, density and base surface, so the figure can be explained later.
Why does survey stock differ from book stock?
Book stock is calculated from production and sales records, which miss spillage, internal transfers and moisture changes. Survey stock measures what is actually on the ground, converted with a density that varies. A small, steady gap is normal. A growing gap points to a measurement problem, a stale density or real loss.
How often should stockpiles be measured for audit?
At least at each financial year end, and often monthly to support month-end reporting. Auditors may want to observe the count or see evidence of it, so plan the year-end survey with them. Monthly measurement also shows trends that a single year-end count cannot.
What density should be used for stockpile tonnage?
Use a bulk density tested on your own material, at its usual moisture and compaction, rather than a generic library figure. Record it, and use the same value across the team until it is retested. A density of 1.6 against 1.8 t/m³ changes the tonnage by 12% on the same volume.
Who should sign off the stock number?
A named person who understands both the survey and the books, often the site manager or survey lead with the finance lead. They should check the base surfaces, the densities and the reconciliation before the figure is booked. That sign-off is part of the trail an auditor will ask about.
About the author
This guide was written by the Birdi team. Birdi (birdi.io) is a geospatial AI workspace that quarry, mining and construction teams use to share drone surveys, volumes and site data in one map. We checked every product fact against each vendor's own website or help center, and read the PCAOB sources, on October 7, 2026.
Related reading
- How to reconcile stockpile volumes: the month-end routine, step by step.
- Stockpile volume software: the wider set of stockpile platforms.
- Choosing stockpile volume software: seven questions to ask any vendor.
- Creating a stockpile volume report: a step-by-step volume report.
Sources
Standards and statistics
- Public Company Accounting Oversight Board. "AS 2510: Auditing Inventories." https://pcaobus.org/oversight/standards/auditing-standards/details/AS2510
- Public Company Accounting Oversight Board. "Auditing Inventories." Briefing paper, SEIAG meeting, November 2023. https://assets.pcaobus.org/pcaob-dev/docs/default-source/about/advisory/documents/seiag-nov.-2023/briefing-paper---auditing-inventory.pdf
- U.S. Geological Survey. "Stone (Crushed)." Mineral Commodity Summaries 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-stone-crushed.pdf
Vendor documentation (read October 7, 2026)
- Birdi Help Center. "How to calculate stockpile tonnage in Birdi." https://help.birdi.io/en/articles/16590329
- Birdi Help Center. "How to compare stockpile volumes between two surveys in Birdi." https://help.birdi.io/en/articles/16591511
- Birdi Help Center. "How accurate is the volumetric calculator?" and "How to use table view for your volumetric layers." https://help.birdi.io/en/articles/10504763
- Birdi. "Pricing." https://www.birdi.io/pricing
- Stockpile Reports. "Plans and Pricing." https://www.stockpilereports.com/pricing.html
- Propeller. "Mining." https://www.propelleraero.com/mining/
- DroneDeploy. "Pricing." https://www.dronedeploy.com/pricing
- QuarryLink. https://www.quarrylink.com.au/
