Can I just use my phone instead of a handheld GPS?

For most geocaching, yes. A dedicated handheld still earns its place with a rated 3-5 m fix under open sky — 1-3 m with EGNOS/WAAS — and with battery life a phone cannot match on a long day.

Is an N95 enough for an abandoned building?

For light dust, yes: N95 blocks 95% of 0.3 µm particles, comparable to FFP2 at 94%. Where dust is heavy and fine, step up to P3 at 99.95% — and remember no particle filter helps against gases or low oxygen.

How close can my new cache be to one that already exists?

No closer than 161 m (0.10 mile). Measure the gap on the cache map before carrying a container out; saturation is the standard reason new listings are refused.

How much water do I need for a summer hunt?

About 0.5 L per hour of walking — 2 L for a 4-hour day, rising to 3-4 L above 30 °C. Water is one of the ten essentials, not an optional extra.

161 mminimum separation between published geocaches

3-5 mhandheld GPS position error under open sky

20-30 Ldaypack volume that holds the ten essentials

4official geocache size classes

What to pack, and why

Modern World Exploration — Beginner | modernworldexploration.com

The short answer: a GPS that fixes you within 3-5 m, a headlamp with a measured runtime, a respirator matched to the dust, and a 20-30 L daypack holding the ten essentials. The longer answer is matching each piece to the session — cache size classes, the 161 m rule, filtration percentages and map scale — which is what this page does, number by number.

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Independent field reference — geocaching, urban exploration, navigation.
Beginner field guides to geocaching, urban exploration and map-and-GPS navigation.

By the numbers

The numbers that decide a session

4official geocache size classesMicro, small, regular and large span containers from under 10 cm to over 40 cm in length.

99.95%P3 respirator filtrationThe highest of the three common ratings, against FFP2 at 94% and N95 at 95% of 0.3 µm particles.

250 mground distance per 1 cm at 1:25,000One centimetre on a standard topo sheet equals 250 m on the ground, with contours every 10 m of elevation.

Specifications worth memorising

Core specifications for a beginner's geocaching and urban exploration kit.
Item	Rating or size	What it means in the field
Micro geocache	Under 10 cm	Log sheet only — bring your own pen
Regular geocache	20-40 cm	Lunchbox class with room for trade items
Cache separation	161 m (0.10 mile)	Minimum gap between two published caches
Handheld GPS	3-5 m accuracy	Tightens to 1-3 m with EGNOS/WAAS corrections
FFP2 respirator	At least 94% filtration	Baseline for dusty interiors
P3 respirator	99.95% filtration	For heavy, fine dust
Headlamp on high	500 lumens, 2-3 h	Per 3,400 mAh 18650 cell
Water carry	0.5 L per hour	2 L for 4 h; 3-4 L above 30 °C

Core specifications for a beginner's geocaching and urban exploration kit.

The pack: ten essentials in 20-30 litres

One 20-30 L daypack carries the standard ten essentials for both hobbies.

The ten essentials are a checklist, not a brand list: navigation, light, first aid, sun protection, a knife, fire, shelter, food, water and clothing. A 20-30 L daypack holds all ten with room to spare.

Water is the most under-packed item. Budget about 0.5 L per hour of walking: a 4-hour summer hunt needs 2 L, rising to 3-4 L once the temperature passes 30 °C.

Light follows the same arithmetic. A 500-lumen headlamp drains a 3,400 mAh 18650 cell in roughly 2-3 hours on high, so carry a spare cell or drop to 200-300 lumens, which is enough for a marked trail.

Navigation — map plus GPS
Light — headlamp and spare cell
First aid kit
Sun protection
Knife or multi-tool
Fire — lighter or matches
Emergency shelter

Terms a beginner will meet

Geocache: A hidden container holding at least a log for finders to sign, classified by length into micro, small, regular and large.
FFP2: A European respirator class filtering at least 94% of airborne particles — the baseline for dusty interiors.
P3: The highest common filter class at 99.95% of particles, chosen where fine dust is heavy.
EGNOS / WAAS: Satellite correction services that tighten a handheld GPS fix from 3-5 m to about 1-3 m under open sky.
Contour interval: The vertical step between neighbouring contour lines — 10 m on a 1:25,000 topographic map.

Objections heard from first-timers

Can I just use my phone instead of a handheld GPS?: For most geocaching, yes. A dedicated handheld still earns its place with a rated 3-5 m fix under open sky — 1-3 m with EGNOS/WAAS — and with battery life a phone cannot match on a long day.
Is an N95 enough for an abandoned building?: For light dust, yes: N95 blocks 95% of 0.3 µm particles, comparable to FFP2 at 94%. Where dust is heavy and fine, step up to P3 at 99.95% — and remember no particle filter helps against gases or low oxygen.
How close can my new cache be to one that already exists?: No closer than 161 m (0.10 mile). Measure the gap on the cache map before carrying a container out; saturation is the standard reason new listings are refused.
How much water do I need for a summer hunt?: About 0.5 L per hour of walking — 2 L for a 4-hour day, rising to 3-4 L above 30 °C. Water is one of the ten essentials, not an optional extra.

How this guide was assembled

Every figure on this page is taken from published geocache listing rules, respirator certification classes and rated equipment specifications. Where a number depends on conditions — battery runtime, GPS accuracy — the full range is quoted rather than a best case. No claim here comes from a retailer or a manufacturer.

Sources and standards

Figures derive from published geocache listing guidelines, European and American respirator classes, and standard topographic map conventions.