# DOCS II vs Sentinel Pro

The clearest difference is update cadence: Sentinel Pro at every 3 weeks against DOCS II's every 58 months. Sentinel Pro also leads on iOS requirement (13.0 vs 15.0). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

DOCS II ships an update every 58 months, Sentinel Pro every 3 weeks. The most recent releases landed on October 19, 2026 and October 8, 2026 respectively.

## The numbers

| Metric | DOCS II | Sentinel Pro |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/docs-ii/id1546600318/reviews)** | — |
| Number of ratings | **1** | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 58 months | **Every 3 weeks** |
| Monetization | Free | — |
| Size | 91 MB | 3 MB |
| Requires iOS | 15.0 | **13.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Virtual Technology LLC](https://appshunter.io/developer/1546600320) | [Ben Software Ltd](https://appshunter.io/developer/1142125927) |

## What reviewers say

### DOCS II

[App page](https://appshunter.io/ios/app/docs-ii/id1546600318)

This app automates the capture and reporting of visible emission observations for air quality compliance. It uses location data, weather, and sun angles to document opacity levels, helping users avoid costly fines. The tool generates compliance archives for regulated sources.

**Highlights:** Automated Visible Emission Observation (VEO) capture, Integration with Google Maps, compass, and inclinometers, Real-time weather and sun angle data, Opacity level documentation, Automated VEO report generation, Compliance archive creation

**Features:** macOS Compatibility

**In-app purchases:** none


### Sentinel Pro

[App page](https://appshunter.io/ios/app/sentinel-pro/id1581444500)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is DOCS II free?

DOCS II is free to download, with no in-app purchases.

### Is Sentinel Pro free?

Sentinel Pro is free to download, with no in-app purchases.

### Do DOCS II or Sentinel Pro have ads?

Neither DOCS II nor Sentinel Pro shows ads.

### Which is updated more often, DOCS II or Sentinel Pro?

DOCS II ships an update every 58 months, and Sentinel Pro every 3 weeks. Most recently, DOCS II was updated on October 19, 2026 and Sentinel Pro on October 8, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*