CRS / EPSG / UTM Guidance

Projection choice is part of every download request and has direct impact on output quality and downstream consistency.

Where You Set CRS/EPSG

• In the dashboard, choose EPSG Projection on the download form.
• In API downloads, set EpsgProjection in the request payload.
• Keep the same EPSG across a time-series when you want stable pixel alignment over time.

Composite and tile/minitile download workflows support UTM EPSG handling through:

• explicit UTM EPSGs (326xx / 327xx), or
• 47000 (auto-EPSG mode), where ClearSKY selects the most suitable UTM EPSG for the request.

Recommended Default for Highest Quality

Prefer UTM EPSG outputs (326xx / 327xx) for most quality-sensitive workflows.

Why this is usually best:

• Better geometric consistency for local/regional AOIs.
• More predictable reprojection behavior.
• Less avoidable resampling than broad/global projections.

Auto-EPSG Mode (47000)

Use 47000 when you want ClearSKY to choose the most suitable UTM EPSG automatically.

This is useful when you want UTM-quality outputs without manually selecting a zone per request.

Cross-Zone AOIs (UTM Transition Areas)

If your AOI crosses UTM zone boundaries, decide these outcomes first:

• Do you want one complete output footprint, or strict single-zone-only data?
• Is exact pixel size in meters more important than minimizing geometric warping effects?
• Should downstream processing treat zone boundaries as one merged surface or separate zone-faithful areas?

Screenshot: three neighboring UTM zones with overlapping ClearSKY tiles near transition boundaries.

UTM-Specific API Controls

UtmDataSelectionMode and UtmGridForcePixelResolutionSize are relevant for UTM-aware output behavior, including explicit UTM EPSGs and auto-EPSG (47000) workflows.

UtmDataSelectionMode

Value	Behavior	Use when
single_utm_fully_covered	Strictly requires polygon coverage from data in the requested EPSG only. No cross-zone fill.	You want strict zone purity and do not want pixels reprojected from neighboring zones.
combined_utm	Uses requested-EPSG pixels first, then fills uncovered parts with pixels reprojected from other EPSGs into the requested EPSG.	You want one complete output for AOIs crossing UTM boundaries.
single_utm	Uses only requested-EPSG pixels, but keeps output array dimensions aligned to the combined_utm footprint (without filling from other EPSGs).	You want requested-zone-only pixels while keeping a predictable output footprint.

UtmGridForcePixelResolutionSize

This flag only affects results when reprojection is involved.

Value	Behavior
true	Forces pixel size to remain exactly Resolution meters. Reprojection effects show up as geometric warping (for example slight twisting).
false	Allows pixel size to deviate slightly from Resolution (for example 9.99 m vs 10 m). Reprojection effects show up as slight pixel-size differences.

Practical Workflow

1. Start with either an explicit UTM EPSG (326xx/327xx) or auto-EPSG (47000) for the main area.
2. Run availability and estimate with the exact same EpsgProjection, UtmDataSelectionMode, and band/model settings you will use for download.
3. For AOIs near zone edges, test at least two mode combinations on a small sample before bulk runs.
4. Lock projection and UTM-mode choices before production time-series jobs.

Visual Validation Tools

For zone-edge planning and tile context, use:

• tiles.clearsky.vision to inspect ClearSKY and Sentinel-2 tile layouts.
• Define an Area with Tiles and Minitiles Ordering for GUID-based selection workflows.

Related: Composite downloads and Tile and Minitile downloads.